diff --git a/dom/base/nsFrameLoader.cpp b/dom/base/nsFrameLoader.cpp
index 57fb9c8c1447..4ffa58ca012d 100644
--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -936,13 +936,13 @@ nsFrameLoader::SwapWithOtherRemoteLoader(nsFrameLoader* aOther,
   mRemoteBrowser->SetBrowserDOMWindow(otherBrowserDOMWindow);
 
   // Native plugin windows used by this remote content need to be reparented.
-  const nsTArray<mozilla::plugins::PPluginWidgetParent*>& plugins =
-    aOther->mRemoteBrowser->ManagedPPluginWidgetParent();
   nsPIDOMWindow* newWin = ourDoc->GetWindow();
   if (newWin) {
     nsRefPtr<nsIWidget> newParent = ((nsGlobalWindow*)newWin)->GetMainWidget();
-    for (uint32_t idx = 0; idx < plugins.Length(); ++idx) {
-      static_cast<mozilla::plugins::PluginWidgetParent*>(plugins[idx])->SetParent(newParent);
+    const ManagedContainer<mozilla::plugins::PPluginWidgetParent>& plugins =
+      aOther->mRemoteBrowser->ManagedPPluginWidgetParent();
+    for (auto iter = plugins.ConstIter(); !iter.Done(); iter.Next()) {
+      static_cast<mozilla::plugins::PluginWidgetParent*>(iter.Get()->GetKey())->SetParent(newParent);
     }
   }
 
diff --git a/dom/indexedDB/ActorsParent.cpp b/dom/indexedDB/ActorsParent.cpp
index 39a22f6c716d..478048aeb10c 100644
--- a/dom/indexedDB/ActorsParent.cpp
+++ b/dom/indexedDB/ActorsParent.cpp
@@ -19888,7 +19888,7 @@ FactoryOp::CheckAtLeastOneAppHasPermission(ContentParent* aContentParent,
   MOZ_ASSERT(!aPermissionString.IsEmpty());
 
 #ifdef MOZ_CHILD_PERMISSIONS
-  const nsTArray<PBrowserParent*>& browsers =
+  const ManagedContainer<PBrowserParent>& browsers =
     aContentParent->ManagedPBrowserParent();
 
   if (!browsers.IsEmpty()) {
@@ -19912,11 +19912,9 @@ FactoryOp::CheckAtLeastOneAppHasPermission(ContentParent* aContentParent,
     const nsPromiseFlatCString permissionString =
       PromiseFlatCString(aPermissionString);
 
-    for (uint32_t index = 0, count = browsers.Length();
-         index < count;
-         index++) {
+    for (auto iter = browsers.ConstIter(); !iter.Done(); iter.Next()) {
       uint32_t appId =
-        TabParent::GetFrom(browsers[index])->OwnOrContainingAppId();
+        TabParent::GetFrom(iter.Get()->GetKey())->OwnOrContainingAppId();
       MOZ_ASSERT(appId != nsIScriptSecurityManager::UNKNOWN_APP_ID &&
                  appId != nsIScriptSecurityManager::NO_APP_ID);
 
diff --git a/dom/ipc/ContentBridgeParent.cpp b/dom/ipc/ContentBridgeParent.cpp
index 8754f9b0beb2..5cfde1393c0a 100644
--- a/dom/ipc/ContentBridgeParent.cpp
+++ b/dom/ipc/ContentBridgeParent.cpp
@@ -166,7 +166,7 @@ ContentBridgeParent::DeallocPBrowserParent(PBrowserParent* aParent)
 void
 ContentBridgeParent::NotifyTabDestroyed()
 {
-  int32_t numLiveTabs = ManagedPBrowserParent().Length();
+  int32_t numLiveTabs = ManagedPBrowserParent().Count();
   if (numLiveTabs == 1) {
     MessageLoop::current()->PostTask(
       FROM_HERE,
diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index 4c5f4276d181..4e729e1b874e 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -1279,7 +1279,7 @@ static void FirstIdle(void)
 mozilla::jsipc::PJavaScriptChild *
 ContentChild::AllocPJavaScriptChild()
 {
-    MOZ_ASSERT(!ManagedPJavaScriptChild().Length());
+    MOZ_ASSERT(ManagedPJavaScriptChild().IsEmpty());
 
     return nsIContentChild::AllocPJavaScriptChild();
 }
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 7352d9da646e..a52b73e13ce9 100755
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -1797,11 +1797,11 @@ ContentParent::ShutDownProcess(ShutDownMethod aMethod)
         }
     }
 
-    const InfallibleTArray<POfflineCacheUpdateParent*>& ocuParents =
+    const ManagedContainer<POfflineCacheUpdateParent>& ocuParents =
         ManagedPOfflineCacheUpdateParent();
-    for (uint32_t i = 0; i < ocuParents.Length(); ++i) {
+    for (auto iter = ocuParents.ConstIter(); !iter.Done(); iter.Next()) {
         nsRefPtr<mozilla::docshell::OfflineCacheUpdateParent> ocuParent =
-            static_cast<mozilla::docshell::OfflineCacheUpdateParent*>(ocuParents[i]);
+            static_cast<mozilla::docshell::OfflineCacheUpdateParent*>(iter.Get()->GetKey());
         ocuParent->StopSendingMessagesToChild();
     }
 
@@ -3418,7 +3418,7 @@ ContentParent::RecvGetXPCOMProcessAttributes(bool* aIsOffline,
 mozilla::jsipc::PJavaScriptParent *
 ContentParent::AllocPJavaScriptParent()
 {
-    MOZ_ASSERT(!ManagedPJavaScriptParent().Length());
+    MOZ_ASSERT(ManagedPJavaScriptParent().IsEmpty());
     return nsIContentParent::AllocPJavaScriptParent();
 }
 
diff --git a/dom/ipc/ContentProcessManager.cpp b/dom/ipc/ContentProcessManager.cpp
index 594975696c9e..403fbb852098 100644
--- a/dom/ipc/ContentProcessManager.cpp
+++ b/dom/ipc/ContentProcessManager.cpp
@@ -290,10 +290,9 @@ ContentProcessManager::GetTabParentByProcessAndTabId(const ContentParentId& aChi
     return nullptr;
   }
 
-  const InfallibleTArray<PBrowserParent*>& browsers =
-    iter->second.mCp->ManagedPBrowserParent();
-  for (uint32_t i = 0; i < browsers.Length(); i++) {
-    nsRefPtr<TabParent> tab = TabParent::GetFrom(browsers[i]);
+  const ManagedContainer<PBrowserParent>& browsers = iter->second.mCp->ManagedPBrowserParent();
+  for (auto iter = browsers.ConstIter(); !iter.Done(); iter.Next()) {
+    nsRefPtr<TabParent> tab = TabParent::GetFrom(iter.Get()->GetKey());
     if (tab->GetTabId() == aChildTabId) {
       return tab.forget();
     }
diff --git a/dom/ipc/CrashReporterChild.cpp b/dom/ipc/CrashReporterChild.cpp
index bc6b94f24ab2..27d3dee2ddd2 100644
--- a/dom/ipc/CrashReporterChild.cpp
+++ b/dom/ipc/CrashReporterChild.cpp
@@ -17,7 +17,7 @@ namespace dom {
 PCrashReporterChild*
 CrashReporterChild::GetCrashReporter()
 {
-  const InfallibleTArray<PCrashReporterChild*>* reporters = nullptr;
+  const ManagedContainer<PCrashReporterChild>* reporters = nullptr;
   switch (XRE_GetProcessType()) {
     case GeckoProcessType_Content: {
       ContentChild* child = ContentChild::GetSingleton();
diff --git a/dom/ipc/ProcessPriorityManager.cpp b/dom/ipc/ProcessPriorityManager.cpp
index c3a489658385..ee2d7cda9c41 100644
--- a/dom/ipc/ProcessPriorityManager.cpp
+++ b/dom/ipc/ProcessPriorityManager.cpp
@@ -1041,11 +1041,11 @@ ParticularProcessPriorityManager::Notify(nsITimer* aTimer)
 bool
 ParticularProcessPriorityManager::HasAppType(const char* aAppType)
 {
-  const InfallibleTArray<PBrowserParent*>& browsers =
+  const ManagedContainer<PBrowserParent>& browsers =
     mContentParent->ManagedPBrowserParent();
-  for (uint32_t i = 0; i < browsers.Length(); i++) {
+  for (auto iter = browsers.ConstIter(); !iter.Done(); iter.Next()) {
     nsAutoString appType;
-    TabParent::GetFrom(browsers[i])->GetAppType(appType);
+    TabParent::GetFrom(iter.Get()->GetKey())->GetAppType(appType);
     if (appType.EqualsASCII(aAppType)) {
       return true;
     }
@@ -1057,10 +1057,10 @@ ParticularProcessPriorityManager::HasAppType(const char* aAppType)
 bool
 ParticularProcessPriorityManager::IsExpectingSystemMessage()
 {
-  const InfallibleTArray<PBrowserParent*>& browsers =
+  const ManagedContainer<PBrowserParent>& browsers =
     mContentParent->ManagedPBrowserParent();
-  for (uint32_t i = 0; i < browsers.Length(); i++) {
-    TabParent* tp = TabParent::GetFrom(browsers[i]);
+  for (auto iter = browsers.ConstIter(); !iter.Done(); iter.Next()) {
+    TabParent* tp = TabParent::GetFrom(iter.Get()->GetKey());
     nsCOMPtr<nsIMozBrowserFrame> bf = do_QueryInterface(tp->GetOwnerElement());
     if (!bf) {
       continue;
@@ -1089,10 +1089,10 @@ ParticularProcessPriorityManager::ComputePriority()
   }
 
   bool isVisible = false;
-  const InfallibleTArray<PBrowserParent*>& browsers =
+  const ManagedContainer<PBrowserParent>& browsers =
     mContentParent->ManagedPBrowserParent();
-  for (uint32_t i = 0; i < browsers.Length(); i++) {
-    if (TabParent::GetFrom(browsers[i])->IsVisible()) {
+  for (auto iter = browsers.ConstIter(); !iter.Done(); iter.Next()) {
+    if (TabParent::GetFrom(iter.Get()->GetKey())->IsVisible()) {
       isVisible = true;
       break;
     }
diff --git a/dom/ipc/TabParent.cpp b/dom/ipc/TabParent.cpp
index a35d74d5eee1..ffae8041a142 100644
--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -563,9 +563,11 @@ TabParent::DestroyInternal()
   // Let all PluginWidgets know we are tearing down. Prevents
   // these objects from sending async events after the child side
   // is shut down.
-  const nsTArray<PPluginWidgetParent*>& kids = ManagedPPluginWidgetParent();
-  for (uint32_t idx = 0; idx < kids.Length(); ++idx) {
-      static_cast<mozilla::plugins::PluginWidgetParent*>(kids[idx])->ParentDestroy();
+  const ManagedContainer<PPluginWidgetParent>& kids =
+    ManagedPPluginWidgetParent();
+  for (auto iter = kids.ConstIter(); !iter.Done(); iter.Next()) {
+    static_cast<mozilla::plugins::PluginWidgetParent*>(
+       iter.Get()->GetKey())->ParentDestroy();
   }
 }
 
@@ -1446,17 +1448,16 @@ TabParent::GetTopLevelDocAccessible() const
 #ifdef ACCESSIBILITY
   // XXX Consider managing non top level PDocAccessibles with their parent
   // document accessible.
-  const nsTArray<PDocAccessibleParent*>& docs = ManagedPDocAccessibleParent();
-  size_t docCount = docs.Length();
-  for (size_t i = 0; i < docCount; i++) {
-    auto doc = static_cast<a11y::DocAccessibleParent*>(docs[i]);
+  const ManagedContainer<PDocAccessibleParent>& docs = ManagedPDocAccessibleParent();
+  for (auto iter = docs.ConstIter(); !iter.Done(); iter.Next()) {
+    auto doc = static_cast<a11y::DocAccessibleParent*>(iter.Get()->GetKey());
     if (!doc->ParentDoc()) {
       return doc;
     }
   }
 
-  MOZ_ASSERT(docCount == 0, "If there isn't a top level accessible doc "
-                             "there shouldn't be an accessible doc at all!");
+  MOZ_ASSERT(docs.Count() == 0, "If there isn't a top level accessible doc "
+                                "there shouldn't be an accessible doc at all!");
 #endif
   return nullptr;
 }
diff --git a/dom/media/gmp/GMPContentChild.cpp b/dom/media/gmp/GMPContentChild.cpp
index 4d9643fcd76d..8cb03e4a1272 100644
--- a/dom/media/gmp/GMPContentChild.cpp
+++ b/dom/media/gmp/GMPContentChild.cpp
@@ -181,28 +181,28 @@ void
 GMPContentChild::CloseActive()
 {
   // Invalidate and remove any remaining API objects.
-  const nsTArray<PGMPAudioDecoderChild*>& audioDecoders =
+  const ManagedContainer<PGMPAudioDecoderChild>& audioDecoders =
     ManagedPGMPAudioDecoderChild();
-  for (uint32_t i = audioDecoders.Length(); i > 0; i--) {
-    audioDecoders[i - 1]->SendShutdown();
+  for (auto iter = audioDecoders.ConstIter(); !iter.Done(); iter.Next()) {
+    iter.Get()->GetKey()->SendShutdown();
   }
 
-  const nsTArray<PGMPDecryptorChild*>& decryptors =
+  const ManagedContainer<PGMPDecryptorChild>& decryptors =
     ManagedPGMPDecryptorChild();
-  for (uint32_t i = decryptors.Length(); i > 0; i--) {
-    decryptors[i - 1]->SendShutdown();
+  for (auto iter = decryptors.ConstIter(); !iter.Done(); iter.Next()) {
+    iter.Get()->GetKey()->SendShutdown();
   }
 
-  const nsTArray<PGMPVideoDecoderChild*>& videoDecoders =
+  const ManagedContainer<PGMPVideoDecoderChild>& videoDecoders =
     ManagedPGMPVideoDecoderChild();
-  for (uint32_t i = videoDecoders.Length(); i > 0; i--) {
-    videoDecoders[i - 1]->SendShutdown();
+  for (auto iter = videoDecoders.ConstIter(); !iter.Done(); iter.Next()) {
+    iter.Get()->GetKey()->SendShutdown();
   }
 
-  const nsTArray<PGMPVideoEncoderChild*>& videoEncoders =
+  const ManagedContainer<PGMPVideoEncoderChild>& videoEncoders =
     ManagedPGMPVideoEncoderChild();
-  for (uint32_t i = videoEncoders.Length(); i > 0; i--) {
-    videoEncoders[i - 1]->SendShutdown();
+  for (auto iter = videoEncoders.ConstIter(); !iter.Done(); iter.Next()) {
+    iter.Get()->GetKey()->SendShutdown();
   }
 }
 
diff --git a/gfx/layers/ipc/CompositorChild.cpp b/gfx/layers/ipc/CompositorChild.cpp
index 655b2fab00fe..60c4bb7aa7c5 100644
--- a/gfx/layers/ipc/CompositorChild.cpp
+++ b/gfx/layers/ipc/CompositorChild.cpp
@@ -92,11 +92,11 @@ CompositorChild::Destroy()
     mLayerManager = nullptr;
   }
 
-  // start from the end of the array because Destroy() can cause the
-  // LayerTransactionChild to be removed from the array.
-  for (int i = ManagedPLayerTransactionChild().Length() - 1; i >= 0; --i) {
+  nsAutoTArray<PLayerTransactionChild*, 16> transactions;
+  ManagedPLayerTransactionChild(transactions);
+  for (int i = transactions.Length() - 1; i >= 0; --i) {
     RefPtr<LayerTransactionChild> layers =
-      static_cast<LayerTransactionChild*>(ManagedPLayerTransactionChild()[i]);
+      static_cast<LayerTransactionChild*>(transactions[i]);
     layers->Destroy();
   }
 
diff --git a/gfx/layers/ipc/CompositorParent.cpp b/gfx/layers/ipc/CompositorParent.cpp
index fa7749a31602..b4ac44acb968 100644
--- a/gfx/layers/ipc/CompositorParent.cpp
+++ b/gfx/layers/ipc/CompositorParent.cpp
@@ -612,7 +612,7 @@ CompositorParent::~CompositorParent()
 void
 CompositorParent::Destroy()
 {
-  MOZ_ASSERT(ManagedPLayerTransactionParent().Length() == 0,
+  MOZ_ASSERT(ManagedPLayerTransactionParent().Count() == 0,
              "CompositorParent destroyed before managed PLayerTransactionParent");
 
   MOZ_ASSERT(mPaused); // Ensure RecvWillStop was called
diff --git a/gfx/layers/ipc/LayerTransactionChild.cpp b/gfx/layers/ipc/LayerTransactionChild.cpp
index c61c9c94e601..1e456c4a22db 100644
--- a/gfx/layers/ipc/LayerTransactionChild.cpp
+++ b/gfx/layers/ipc/LayerTransactionChild.cpp
@@ -33,11 +33,12 @@ LayerTransactionChild::Destroy()
   // When it happens, IPCOpen() is still true.
   // See bug 1004191.
   mDestroyed = true;
-  MOZ_ASSERT(0 == ManagedPLayerChild().Length(),
+  MOZ_ASSERT(0 == ManagedPLayerChild().Count(),
              "layers should have been cleaned up by now");
 
-  for (size_t i = 0; i < ManagedPTextureChild().Length(); ++i) {
-    TextureClient* texture = TextureClient::AsTextureClient(ManagedPTextureChild()[i]);
+  const ManagedContainer<PTextureChild>& textures = ManagedPTextureChild();
+  for (auto iter = textures.ConstIter(); !iter.Done(); iter.Next()) {
+    TextureClient* texture = TextureClient::AsTextureClient(iter.Get()->GetKey());
     if (texture) {
       texture->ForceRemove();
     }
diff --git a/gfx/layers/ipc/LayerTransactionParent.cpp b/gfx/layers/ipc/LayerTransactionParent.cpp
index 7f30eeef5cff..eee59ae7f3f6 100644
--- a/gfx/layers/ipc/LayerTransactionParent.cpp
+++ b/gfx/layers/ipc/LayerTransactionParent.cpp
@@ -175,9 +175,10 @@ void
 LayerTransactionParent::Destroy()
 {
   mDestroyed = true;
-  for (size_t i = 0; i < ManagedPLayerParent().Length(); ++i) {
+  const ManagedContainer<PLayerParent>& layers = ManagedPLayerParent();
+  for (auto iter = layers.ConstIter(); !iter.Done(); iter.Next()) {
     ShadowLayerParent* slp =
-      static_cast<ShadowLayerParent*>(ManagedPLayerParent()[i]);
+      static_cast<ShadowLayerParent*>(iter.Get()->GetKey());
     slp->Destroy();
   }
 }
diff --git a/ipc/glue/ProtocolUtils.h b/ipc/glue/ProtocolUtils.h
index b501682b69f4..c68990cedc10 100644
--- a/ipc/glue/ProtocolUtils.h
+++ b/ipc/glue/ProtocolUtils.h
@@ -28,6 +28,9 @@
 #include <android/log.h>
 #endif
 
+template<typename T> class nsTHashtable;
+template<typename T> class nsPtrHashKey;
+
 // WARNING: this takes into account the private, special-message-type
 // enum in ipc_channel.h.  They need to be kept in sync.
 namespace {
@@ -328,14 +331,18 @@ DuplicateHandle(HANDLE aSourceHandle,
 
 } // namespace ipc
 
+template<typename Protocol>
+using ManagedContainer = nsTHashtable<nsPtrHashKey<Protocol>>;
+
 template<typename Protocol>
 Protocol*
-LoneManagedOrNull(const nsTArray<Protocol*>& aManagees)
+LoneManagedOrNull(const ManagedContainer<Protocol>& aManagees)
 {
-    if (aManagees.Length() == 0) {
+    if (aManagees.IsEmpty()) {
         return nullptr;
     }
-    return aManagees[0];
+    MOZ_ASSERT(aManagees.Count() == 1);
+    return aManagees.ConstIter().Get()->GetKey();
 }
 
 } // namespace mozilla
diff --git a/ipc/ipdl/ipdl/builtin.py b/ipc/ipdl/ipdl/builtin.py
index b141df9fb547..c9893566f6b4 100644
--- a/ipc/ipdl/ipdl/builtin.py
+++ b/ipc/ipdl/ipdl/builtin.py
@@ -50,6 +50,7 @@ HeaderIncludes = (
     'nsStringGlue.h',
     'nsTArray.h',
     'mozilla/ipc/ProtocolUtils.h',
+    'nsTHashtable.h',
 )
 
 CppIncludes = (
diff --git a/ipc/ipdl/ipdl/lower.py b/ipc/ipdl/ipdl/lower.py
index 6f32e2c93707..3b49dde4a7e4 100644
--- a/ipc/ipdl/ipdl/lower.py
+++ b/ipc/ipdl/ipdl/lower.py
@@ -335,6 +335,10 @@ def _refptrTake(expr):
 def _cxxArrayType(basetype, const=0, ref=0):
     return Type('nsTArray', T=basetype, const=const, ref=ref, hasimplicitcopyctor=False)
 
+def _cxxManagedContainerType(basetype, const=0, ref=0):
+    return Type('ManagedContainer', T=basetype,
+                const=const, ref=ref, hasimplicitcopyctor=False)
+
 def _cxxFallibleArrayType(basetype, const=0, ref=0):
     return Type('FallibleTArray', T=basetype, const=const, ref=ref)
 
@@ -353,20 +357,18 @@ def _callCxxSwapArrayElements(arr1, arr2, sel='.'):
                     args=[ arr2 ])
 
 def _callInsertManagedActor(managees, actor):
-    return ExprCall(ExprSelect(managees, '.', 'InsertElementSorted'),
+    return ExprCall(ExprSelect(managees, '.', 'PutEntry'),
                     args=[ actor ])
 
 def _callRemoveManagedActor(managees, actor):
-    return ExprCall(ExprSelect(managees, '.', 'RemoveElementSorted'),
+    return ExprCall(ExprSelect(managees, '.', 'RemoveEntry'),
                     args=[ actor ])
 
 def _callClearManagedActors(managees):
     return ExprCall(ExprSelect(managees, '.', 'Clear'))
 
 def _callHasManagedActor(managees, actor):
-    return ExprBinary(
-        ExprSelect(managees, '.', 'NoIndex'), '!=',
-        ExprCall(ExprSelect(managees, '.', 'BinaryIndexOf'), args=[ actor ]))
+    return ExprCall(ExprSelect(managees, '.', 'Contains'), args=[ actor ])
 
 def _otherSide(side):
     if side == 'child':  return 'parent'
@@ -1266,8 +1268,8 @@ class Protocol(ipdl.ast.Protocol):
 
     def managedVarType(self, actortype, side, const=0, ref=0):
         assert self.decl.type.isManagerOf(actortype)
-        return _cxxArrayType(self.managedCxxType(actortype, side),
-                             const=const, ref=ref)
+        return _cxxManagedContainerType(Type(_actorName(actortype.name(), side)),
+                                        const=const, ref=ref)
 
     def managerArrayExpr(self, thisvar, side):
         """The member var my manager keeps of actors of my type."""
@@ -3054,17 +3056,41 @@ class _GenerateProtocolActorCode(ipdl.ast.Visitor):
 
                 self.cls.addstmts([ managermeth, Whitespace.NL ])
 
+        def actorFromIter(itervar):
+            return ExprCall(ExprSelect(ExprCall(ExprSelect(itervar, '.', 'Get')),
+                                       '->', 'GetKey'))
+        def forLoopOverHashtable(hashtable, itervar, const=False):
+            return StmtFor(
+                init=Param(Type.AUTO, itervar.name,
+                           ExprCall(ExprSelect(hashtable, '.', 'ConstIter' if const else 'Iter'))),
+                cond=ExprNot(ExprCall(ExprSelect(itervar, '.', 'Done'))),
+                update=ExprCall(ExprSelect(itervar, '.', 'Next')))
+
         ## Managed[T](Array& inout) const
         ## const Array<T>& Managed() const
         for managed in ptype.manages:
             arrvar = ExprVar('aArr')
             meth = MethodDefn(MethodDecl(
                 p.managedMethod(managed, self.side).name,
-                params=[ Decl(p.managedVarType(managed, self.side, ref=1),
+                params=[ Decl(_cxxArrayType(p.managedCxxType(managed, self.side), ref=1),
                               arrvar.name) ],
                 const=1))
-            meth.addstmt(StmtExpr(ExprAssn(
-                arrvar, p.managedVar(managed, self.side))))
+            ivar = ExprVar('i')
+            elementsvar = ExprVar('elements')
+            itervar = ExprVar('iter')
+            meth.addstmt(StmtDecl(Decl(Type.UINT32, ivar.name),
+                                  init=ExprLiteral.ZERO))
+            meth.addstmt(StmtDecl(Decl(Type(_actorName(managed.name(), self.side), ptrptr=1), elementsvar.name),
+                                  init=ExprCall(ExprSelect(arrvar, '.', 'AppendElements'),
+                                                args=[ ExprCall(ExprSelect(p.managedVar(managed, self.side),
+                                                                           '.', 'Count')) ])))
+            foreachaccumulate = forLoopOverHashtable(p.managedVar(managed, self.side),
+                                                     itervar, const=True)
+            foreachaccumulate.addstmt(StmtExpr(
+                ExprAssn(ExprIndex(elementsvar, ivar),
+                         actorFromIter(itervar))))
+            foreachaccumulate.addstmt(StmtExpr(ExprPrefixUnop(ivar, '++')))
+            meth.addstmt(foreachaccumulate)
 
             refmeth = MethodDefn(MethodDecl(
                 p.managedMethod(managed, self.side).name,
@@ -3404,6 +3430,7 @@ class _GenerateProtocolActorCode(ipdl.ast.Visitor):
         subtreewhyvar = ExprVar('subtreewhy')
         kidsvar = ExprVar('kids')
         ivar = ExprVar('i')
+        itervar = ExprVar('iter')
         ithkid = ExprIndex(kidsvar, ivar)
 
         destroysubtree = MethodDefn(MethodDecl(
@@ -3433,6 +3460,8 @@ class _GenerateProtocolActorCode(ipdl.ast.Visitor):
             ])
 
         for managed in ptype.manages:
+            managedVar = p.managedVar(managed, self.side)
+
             foreachdestroy = StmtFor(
                 init=Param(Type.UINT32, ivar.name, ExprLiteral.ZERO),
                 cond=ExprBinary(ivar, '<', _callCxxArrayLength(kidsvar)),
@@ -3471,20 +3500,16 @@ class _GenerateProtocolActorCode(ipdl.ast.Visitor):
         ## DeallocSubtree()
         deallocsubtree = MethodDefn(MethodDecl(deallocsubtreevar.name))
         for managed in ptype.manages:
-            foreachrecurse = StmtFor(
-                init=Param(Type.UINT32, ivar.name, ExprLiteral.ZERO),
-                cond=ExprBinary(ivar, '<', _callCxxArrayLength(kidsvar)),
-                update=ExprPrefixUnop(ivar, '++'))
-            foreachrecurse.addstmt(StmtExpr(ExprCall(
-                ExprSelect(ithkid, '->', deallocsubtreevar.name))))
+            managedVar = p.managedVar(managed, self.side)
 
-            foreachdealloc = StmtFor(
-                init=Param(Type.UINT32, ivar.name, ExprLiteral.ZERO),
-                cond=ExprBinary(ivar, '<', _callCxxArrayLength(kidsvar)),
-                update=ExprPrefixUnop(ivar, '++'))
+            foreachrecurse = forLoopOverHashtable(managedVar, itervar)
+            foreachrecurse.addstmt(StmtExpr(ExprCall(
+                ExprSelect(actorFromIter(itervar), '->', deallocsubtreevar.name))))
+
+            foreachdealloc = forLoopOverHashtable(managedVar, itervar)
             foreachdealloc.addstmts([
                 StmtExpr(ExprCall(_deallocMethod(managed, self.side),
-                                  args=[ ithkid ]))
+                                  args=[ actorFromIter(itervar) ]))
             ])
 
             block = StmtBlock()
@@ -3492,17 +3517,10 @@ class _GenerateProtocolActorCode(ipdl.ast.Visitor):
                 Whitespace(
                     '// Recursively deleting %s kids\n'% (managed.name()),
                     indent=1),
-                StmtDecl(
-                    Decl(p.managedVarType(managed, self.side, ref=1),
-                         kidsvar.name),
-                    init=p.managedVar(managed, self.side)),
                 foreachrecurse,
                 Whitespace.NL,
-                # no need to copy |kids| here; we're the ones deleting
-                # stragglers, no outside C++ is being invoked (except
-                # Dealloc(subactor))
                 foreachdealloc,
-                StmtExpr(_callClearManagedActors(p.managedVar(managed, self.side))),
+                StmtExpr(_callClearManagedActors(managedVar)),
 
             ])
             deallocsubtree.addstmt(block)
@@ -3561,7 +3579,6 @@ class _GenerateProtocolActorCode(ipdl.ast.Visitor):
 
         for managed in ptype.manages:
             self.cls.addstmts([
-                Whitespace('// Sorted by pointer value\n', indent=1),
                 StmtDecl(Decl(
                     p.managedVarType(managed, self.side),
                     p.managedVar(managed, self.side).name)) ])
diff --git a/ipc/ipdl/test/cxx/TestSelfManageRoot.cpp b/ipc/ipdl/test/cxx/TestSelfManageRoot.cpp
index 564bc814df46..e8b2330ba1f5 100644
--- a/ipc/ipdl/test/cxx/TestSelfManageRoot.cpp
+++ b/ipc/ipdl/test/cxx/TestSelfManageRoot.cpp
@@ -22,21 +22,21 @@ TestSelfManageRootParent::Main()
     if (!a)
         fail("constructing PTestSelfManage");
 
-    ASSERT(1 == ManagedPTestSelfManageParent().Length());
+    ASSERT(1 == ManagedPTestSelfManageParent().Count());
 
     TestSelfManageParent* aa =
         static_cast<TestSelfManageParent*>(a->SendPTestSelfManageConstructor());
     if (!aa)
         fail("constructing PTestSelfManage");
 
-    ASSERT(1 == ManagedPTestSelfManageParent().Length() &&
-           1 == a->ManagedPTestSelfManageParent().Length());
+    ASSERT(1 == ManagedPTestSelfManageParent().Count() &&
+           1 == a->ManagedPTestSelfManageParent().Count());
 
     if (!PTestSelfManageParent::Send__delete__(aa))
         fail("destroying PTestSelfManage");
     ASSERT(Deletion == aa->mWhy &&
-           1 == ManagedPTestSelfManageParent().Length() &&
-           0 == a->ManagedPTestSelfManageParent().Length());
+           1 == ManagedPTestSelfManageParent().Count() &&
+           0 == a->ManagedPTestSelfManageParent().Count());
     delete aa;
 
     aa =
@@ -44,15 +44,15 @@ TestSelfManageRootParent::Main()
     if (!aa)
         fail("constructing PTestSelfManage");
 
-    ASSERT(1 == ManagedPTestSelfManageParent().Length() &&
-           1 == a->ManagedPTestSelfManageParent().Length());
+    ASSERT(1 == ManagedPTestSelfManageParent().Count() &&
+           1 == a->ManagedPTestSelfManageParent().Count());
 
     if (!PTestSelfManageParent::Send__delete__(a))
         fail("destroying PTestSelfManage");
     ASSERT(Deletion == a->mWhy &&
            AncestorDeletion == aa->mWhy &&
-           0 == ManagedPTestSelfManageParent().Length() &&
-           0 == a->ManagedPTestSelfManageParent().Length());
+           0 == ManagedPTestSelfManageParent().Count() &&
+           0 == a->ManagedPTestSelfManageParent().Count());
     delete a;
     delete aa;
 
diff --git a/ipc/ipdl/test/cxx/TestShutdown.cpp b/ipc/ipdl/test/cxx/TestShutdown.cpp
index 217aabc851a5..95a242bff384 100644
--- a/ipc/ipdl/test/cxx/TestShutdown.cpp
+++ b/ipc/ipdl/test/cxx/TestShutdown.cpp
@@ -26,7 +26,7 @@ TestShutdownParent::ActorDestroy(ActorDestroyReason why)
 void
 TestShutdownSubParent::ActorDestroy(ActorDestroyReason why)
 {
-    if (Manager()->ManagedPTestShutdownSubParent().Length() == 0)
+    if (Manager()->ManagedPTestShutdownSubParent().Count() == 0)
         fail("manager should still have managees!");
 
     if (mExpectCrash && AbnormalShutdown != why)
@@ -34,14 +34,14 @@ TestShutdownSubParent::ActorDestroy(ActorDestroyReason why)
     else if (!mExpectCrash && AbnormalShutdown == why)
         fail("wasn't expecting crash!");
 
-    if (mExpectCrash && 0 == ManagedPTestShutdownSubsubParent().Length())
+    if (mExpectCrash && 0 == ManagedPTestShutdownSubsubParent().Count())
         fail("expected to *still* have kids");
 }
 
 void
 TestShutdownSubsubParent::ActorDestroy(ActorDestroyReason why)
 {
-    if (Manager()->ManagedPTestShutdownSubsubParent().Length() == 0)
+    if (Manager()->ManagedPTestShutdownSubsubParent().Count() == 0)
         fail("manager should still have managees!");
 
     if (mExpectParentDeleted && AncestorDeletion != why)
@@ -206,7 +206,7 @@ TestShutdownSubChild::AnswerStackFrame()
 void
 TestShutdownSubChild::ActorDestroy(ActorDestroyReason why)
 {
-    if (Manager()->ManagedPTestShutdownSubChild().Length() == 0)
+    if (Manager()->ManagedPTestShutdownSubChild().Count() == 0)
         fail("manager should still have managees!");
 
     if (mExpectCrash && AbnormalShutdown != why)
@@ -214,14 +214,14 @@ TestShutdownSubChild::ActorDestroy(ActorDestroyReason why)
     else if (!mExpectCrash && AbnormalShutdown == why)
         fail("wasn't expecting crash!");
 
-    if (mExpectCrash && 0 == ManagedPTestShutdownSubsubChild().Length())
+    if (mExpectCrash && 0 == ManagedPTestShutdownSubsubChild().Count())
         fail("expected to *still* have kids");
 }
 
 void
 TestShutdownSubsubChild::ActorDestroy(ActorDestroyReason why)
 {
-    if (Manager()->ManagedPTestShutdownSubsubChild().Length() == 0)
+    if (Manager()->ManagedPTestShutdownSubsubChild().Count() == 0)
         fail("manager should still have managees!");
 
     if (mExpectParentDeleted && AncestorDeletion != why)
diff --git a/widget/gonk/GonkPermission.cpp b/widget/gonk/GonkPermission.cpp
index a456d07f9c52..e72aaabab103 100644
--- a/widget/gonk/GonkPermission.cpp
+++ b/widget/gonk/GonkPermission.cpp
@@ -90,9 +90,11 @@ GonkPermissionChecker::Run()
   }
 
   // Now iterate its apps...
-  for (uint32_t i = 0; i < contentParent->ManagedPBrowserParent().Length(); i++) {
+  const ManagedContainer<PBrowserParent>& browsers =
+    contentParent->ManagedPBrowserParent();
+  for (auto iter = browsers.ConstIter(); !iter.Done(); iter.Next()) {
     dom::TabParent *tabParent =
-      static_cast<dom::TabParent*>(contentParent->ManagedPBrowserParent()[i]);
+      static_cast<dom::TabParent*>(iter.Get()->GetKey());
     nsCOMPtr<mozIApplication> mozApp = tabParent->GetOwnOrContainingApp();
     if (!mozApp) {
       continue;