From 16aea1a321645976b5c859dcc5ec8ccce9afae49 Mon Sep 17 00:00:00 2001
From: Margareta Eliza Balazs <ebalazs@mozilla.com>
Date: Wed, 28 Feb 2018 12:25:31 +0200
Subject: [PATCH] Backed out changeset 283b2a4cb219 (bug 1422653) for bustage
 in
 /builds/worker/workspace/build/src/layout/base/nsCSSFrameConstructor.cpp:6840:26
 on a CLOSED TREE

---
 dom/base/ChildIterator.cpp | 39 ++++++++++++++++----------------------
 dom/base/ChildIterator.h   | 31 +++++++++++-------------------
 2 files changed, 27 insertions(+), 43 deletions(-)

diff --git a/dom/base/ChildIterator.cpp b/dom/base/ChildIterator.cpp
index 058e4b4aa450..1929a05d1b3e 100644
--- a/dom/base/ChildIterator.cpp
+++ b/dom/base/ChildIterator.cpp
@@ -124,7 +124,6 @@ void
 FlattenedChildIterator::Init(bool aIgnoreXBL)
 {
   if (aIgnoreXBL) {
-    mXBLInvolved = Some(false);
     return;
   }
 
@@ -133,7 +132,7 @@ FlattenedChildIterator::Init(bool aIgnoreXBL)
   if (mParent->IsElement()) {
     if (ShadowRoot* shadow = mParent->AsElement()->GetShadowRoot()) {
       mParent = shadow;
-      mXBLInvolved = Some(true);
+      mXBLInvolved = true;
       return;
     }
   }
@@ -144,31 +143,25 @@ FlattenedChildIterator::Init(bool aIgnoreXBL)
   if (binding) {
     MOZ_ASSERT(binding->GetAnonymousContent());
     mParent = binding->GetAnonymousContent();
-    mXBLInvolved = Some(true);
-  }
-}
-
-bool
-FlattenedChildIterator::ComputeWhetherXBLIsInvolved() const
-{
-  MOZ_ASSERT(mXBLInvolved.isNothing());
-  // We set mXBLInvolved to true if either the node we're iterating has a
-  // binding with content attached to it (in which case it is handled in Init),
-  // or the node is generated XBL content and has an <xbl:children> child.
-  if (!mParent->GetBindingParent()) {
-    return false;
+    mXBLInvolved = true;
   }
 
-  for (nsIContent* child = mParent->GetFirstChild();
-       child;
-       child = child->GetNextSibling()) {
-    if (child->NodeInfo()->Equals(nsGkAtoms::children, kNameSpaceID_XBL)) {
-      MOZ_ASSERT(child->GetBindingParent());
-      return true;
+  // We set mXBLInvolved to true if either:
+  // - The node we're iterating has a binding with content attached to it.
+  // - The node is generated XBL content and has an <xbl:children> child.
+  //
+  // FIXME(emilio): This is very slow :(
+  if (!mXBLInvolved && mParent->GetBindingParent()) {
+    for (nsIContent* child = mParent->GetFirstChild();
+         child;
+         child = child->GetNextSibling()) {
+      if (child->NodeInfo()->Equals(nsGkAtoms::children, kNameSpaceID_XBL)) {
+        MOZ_ASSERT(child->GetBindingParent());
+        mXBLInvolved = true;
+        break;
+      }
     }
   }
-
-  return false;
 }
 
 bool
diff --git a/dom/base/ChildIterator.h b/dom/base/ChildIterator.h
index be95b8a54eee..2b20b4e12e71 100644
--- a/dom/base/ChildIterator.h
+++ b/dom/base/ChildIterator.h
@@ -134,6 +134,7 @@ public:
   explicit FlattenedChildIterator(const nsIContent* aParent,
                                   bool aStartAtBeginning = true)
     : ExplicitChildIterator(aParent, aStartAtBeginning)
+    , mXBLInvolved(false)
     , mOriginalContent(aParent)
   {
     Init(false);
@@ -141,30 +142,20 @@ public:
 
   FlattenedChildIterator(FlattenedChildIterator&& aOther)
     : ExplicitChildIterator(Move(aOther))
-    , mOriginalContent(aOther.mOriginalContent)
     , mXBLInvolved(aOther.mXBLInvolved)
+    , mOriginalContent(aOther.mOriginalContent)
   {}
 
   FlattenedChildIterator(const FlattenedChildIterator& aOther)
     : ExplicitChildIterator(aOther)
-    , mOriginalContent(aOther.mOriginalContent)
     , mXBLInvolved(aOther.mXBLInvolved)
+    , mOriginalContent(aOther.mOriginalContent)
   {}
 
-  bool XBLInvolved() {
-    if (mXBLInvolved.isNothing()) {
-      mXBLInvolved = Some(ComputeWhetherXBLIsInvolved());
-    }
-    return *mXBLInvolved;
-  }
+  bool XBLInvolved() { return mXBLInvolved; }
 
   const nsIContent* Parent() const { return mOriginalContent; }
 
-private:
-  bool ComputeWhetherXBLIsInvolved() const;
-
-  void Init(bool aIgnoreXBL);
-
 protected:
   /**
    * This constructor is a hack to help AllChildrenIterator which sometimes
@@ -173,20 +164,20 @@ protected:
   FlattenedChildIterator(const nsIContent* aParent, uint32_t aFlags,
                          bool aStartAtBeginning = true)
     : ExplicitChildIterator(aParent, aStartAtBeginning)
+    , mXBLInvolved(false)
     , mOriginalContent(aParent)
   {
     bool ignoreXBL = aFlags & nsIContent::eAllButXBL;
     Init(ignoreXBL);
   }
 
-  const nsIContent* mOriginalContent;
+  void Init(bool aIgnoreXBL);
 
-private:
-  // For certain optimizations, nsCSSFrameConstructor needs to know if the child
-  // list of the element that we're iterating matches its .childNodes.
-  //
-  // This is lazily computed when asked for it.
-  Maybe<bool> mXBLInvolved;
+  // For certain optimizations, nsCSSFrameConstructor needs to know if the
+  // child list of the element that we're iterating matches its .childNodes.
+  bool mXBLInvolved;
+
+  const nsIContent* mOriginalContent;
 };
 
 /**