diff --git a/accessible/base/NotificationController.cpp b/accessible/base/NotificationController.cpp
index f2ecee82cfb7..d5a678e32141 100644
--- a/accessible/base/NotificationController.cpp
+++ b/accessible/base/NotificationController.cpp
@@ -13,7 +13,6 @@
 #include "TextUpdater.h"
 
 #include "mozilla/dom/BrowserChild.h"
-#include "mozilla/dom/BrowsingContext.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/Telemetry.h"
@@ -767,10 +766,11 @@ void NotificationController::WillRefresh(mozilla::TimeStamp aTime) {
       continue;
     }
 
-    BrowsingContext* bc = childDoc->DocumentNode()->GetBrowsingContext();
-    if (bc && !bc->IsCached() && bc->GetEmbedderElement()) {
-      Accessible* outerDocAcc =
-          mDocument->GetAccessible(bc->GetEmbedderElement());
+    nsIContent* ownerContent =
+        mDocument->DocumentNode()->FindContentForSubDocument(
+            childDoc->DocumentNode());
+    if (ownerContent) {
+      Accessible* outerDocAcc = mDocument->GetAccessible(ownerContent);
       if (outerDocAcc && outerDocAcc->AppendChild(childDoc)) {
         if (mDocument->AppendChildDocument(childDoc)) {
           newChildDocs.AppendElement(std::move(mHangingChildDocuments[idx]));
diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
index 73445fb4fb2b..a3b63c2e46ff 100644
--- a/dom/base/Document.cpp
+++ b/dom/base/Document.cpp
@@ -6724,6 +6724,22 @@ Document* Document::GetSubDocumentFor(nsIContent* aContent) const {
   return nullptr;
 }
 
+Element* Document::FindContentForSubDocument(Document* aDocument) const {
+  NS_ENSURE_TRUE(aDocument, nullptr);
+
+  if (!mSubDocuments) {
+    return nullptr;
+  }
+
+  for (auto iter = mSubDocuments->Iter(); !iter.Done(); iter.Next()) {
+    auto entry = static_cast<SubDocMapEntry*>(iter.Get());
+    if (entry->mSubDocument == aDocument) {
+      return entry->mKey;
+    }
+  }
+  return nullptr;
+}
+
 bool Document::IsNodeOfType(uint32_t aFlags) const { return false; }
 
 Element* Document::GetRootElement() const {
@@ -7508,17 +7524,15 @@ void Document::DispatchContentLoadedEvents() {
   // target_frame is the [i]frame element that will be used as the
   // target for the event. It's the [i]frame whose content is done
   // loading.
-  nsCOMPtr<Element> target_frame;
+  nsCOMPtr<EventTarget> target_frame;
 
-  if (BrowsingContext* bc = GetBrowsingContext()) {
-    if (!bc->IsCached()) {
-      target_frame = bc->GetEmbedderElement();
-    }
+  if (mParentDocument) {
+    target_frame = mParentDocument->FindContentForSubDocument(this);
   }
 
-  if (target_frame && target_frame->IsInComposedDoc()) {
-    nsCOMPtr<Document> parent = target_frame->OwnerDoc();
-    while (parent) {
+  if (target_frame) {
+    nsCOMPtr<Document> parent = mParentDocument;
+    do {
       RefPtr<Event> event;
       if (parent) {
         IgnoredErrorResult ignored;
@@ -7549,7 +7563,7 @@ void Document::DispatchContentLoadedEvents() {
       }
 
       parent = parent->GetInProcessParentDocument();
-    }
+    } while (parent);
   }
 
   // If the document has a manifest attribute, fire a MozApplicationManifest
@@ -14483,10 +14497,7 @@ bool Document::ApplyFullscreen(UniquePtr<FullscreenRequest> aRequest) {
       break;
     }
     Document* parent = child->GetInProcessParentDocument();
-    BrowsingContext* bc = child->GetBrowsingContext();
-    Element* element =
-        bc && !bc->IsCached() ? bc->GetEmbedderElement() : nullptr;
-
+    Element* element = parent->FindContentForSubDocument(child);
     if (!element) {
       // We've reached the root.No more changes need to be made
       // to the top layer stacks of documents further up the tree.
diff --git a/dom/base/Document.h b/dom/base/Document.h
index 71328a90197c..6ad82c390e98 100644
--- a/dom/base/Document.h
+++ b/dom/base/Document.h
@@ -1254,6 +1254,11 @@ class Document : public nsINode,
    */
   Document* GetSubDocumentFor(nsIContent* aContent) const;
 
+  /**
+   * Find the content node for which aDocument is a sub document.
+   */
+  Element* FindContentForSubDocument(Document* aDocument) const;
+
   /**
    * Return the doctype for this document.
    */
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 5c24f5bc76ce..f7a2db0d9381 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -2320,8 +2320,9 @@ nsINode* nsContentUtils::GetCrossDocParentNode(nsINode* aChild) {
     return parent;
   }
 
-  BrowsingContext* bc = aChild->AsDocument()->GetBrowsingContext();
-  return bc && !bc->IsCached() ? bc->GetEmbedderElement() : nullptr;
+  Document* doc = aChild->AsDocument();
+  Document* parentDoc = doc->GetInProcessParentDocument();
+  return parentDoc ? parentDoc->FindContentForSubDocument(doc) : nullptr;
 }
 
 nsINode* nsContentUtils::GetNearestInProcessCrossDocParentNode(
diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index 2f2441c44a7b..c8182255b01d 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -5123,6 +5123,9 @@ void nsGlobalWindowOuter::FocusOuter(CallerType aCallerType) {
     return;
   }
 
+  // Don't look for a presshell if we're a root chrome window that's got
+  // about:blank loaded.  We don't want to focus our widget in that case.
+  // XXXbz should we really be checking for IsInitialDocument() instead?
   RefPtr<BrowsingContext> parent;
   BrowsingContext* bc = GetBrowsingContext();
   if (bc) {
@@ -5145,10 +5148,13 @@ void nsGlobalWindowOuter::FocusOuter(CallerType aCallerType) {
       }
       return;
     }
-    if (!bc->IsCached()) {
-      if (Element* frame = bc->GetEmbedderElement()) {
-        nsContentUtils::RequestFrameFocus(*frame, canFocus, aCallerType);
-      }
+    nsCOMPtr<Document> parentdoc = parent->GetDocument();
+    if (!parentdoc) {
+      return;
+    }
+
+    if (Element* frame = parentdoc->FindContentForSubDocument(mDoc)) {
+      nsContentUtils::RequestFrameFocus(*frame, canFocus, aCallerType);
     }
     return;
   }
diff --git a/dom/events/EventStateManager.cpp b/dom/events/EventStateManager.cpp
index 3c1aa5b73451..b82fc863426e 100644
--- a/dom/events/EventStateManager.cpp
+++ b/dom/events/EventStateManager.cpp
@@ -4501,15 +4501,12 @@ void EventStateManager::NotifyMouseOver(WidgetMouseEvent* aMouseEvent,
   // content associated with our subdocument.
   EnsureDocument(mPresContext);
   if (Document* parentDoc = mDocument->GetInProcessParentDocument()) {
-    if (RefPtr<BrowsingContext> bc = mDocument->GetBrowsingContext()) {
-      if (!bc->IsCached()) {
-        if (nsCOMPtr<nsIContent> docContent = bc->GetEmbedderElement()) {
-          if (PresShell* parentPresShell = parentDoc->GetPresShell()) {
-            RefPtr<EventStateManager> parentESM =
-                parentPresShell->GetPresContext()->EventStateManager();
-            parentESM->NotifyMouseOver(aMouseEvent, docContent);
-          }
-        }
+    if (nsCOMPtr<nsIContent> docContent =
+            parentDoc->FindContentForSubDocument(mDocument)) {
+      if (PresShell* parentPresShell = parentDoc->GetPresShell()) {
+        RefPtr<EventStateManager> parentESM =
+            parentPresShell->GetPresContext()->EventStateManager();
+        parentESM->NotifyMouseOver(aMouseEvent, docContent);
       }
     }
   }
diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
index 72bac3f7e9bc..5f8826a6a3ad 100644
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -680,8 +680,8 @@ nsresult nsPresContext::Init(nsDeviceContext* aDeviceContext) {
       // XXX the document can change in AttachPresShell, does this work?
       dom::BrowsingContext* browsingContext = mDocument->GetBrowsingContext();
       if (browsingContext && !browsingContext->IsTop()) {
-        MOZ_ASSERT(!browsingContext->IsCached());
-        Element* containingElement = browsingContext->GetEmbedderElement();
+        Element* containingElement =
+            parent->FindContentForSubDocument(mDocument);
         if (!containingElement->IsXULElement() ||
             !containingElement->HasAttr(kNameSpaceID_None,
                                         nsGkAtoms::forceOwnRefreshDriver)) {
diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index 7d75d0523cb1..1d2110fc8771 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -821,16 +821,12 @@ bool nsComputedDOMStyle::NeedsToFlushStyle(nsCSSPropertyID aPropID) const {
   // If parent document is there, also needs to check if there is some change
   // that needs to flush this document (e.g. size change for iframe).
   while (doc->StyleOrLayoutObservablyDependsOnParentDocumentLayout()) {
-    if (BrowsingContext* bc = doc->GetBrowsingContext()) {
-      if (Element* element = bc->GetEmbedderElement()) {
-        MOZ_ASSERT(!bc->IsCached());
-        if (ElementNeedsRestyle(element, nullptr, mayNeedToFlushLayout)) {
-          return true;
-        }
-      }
+    Document* parentDocument = doc->GetInProcessParentDocument();
+    Element* element = parentDocument->FindContentForSubDocument(doc);
+    if (ElementNeedsRestyle(element, nullptr, mayNeedToFlushLayout)) {
+      return true;
     }
-
-    doc = doc->GetInProcessParentDocument();
+    doc = parentDocument;
   }
 
   return false;