Bug 1247364 - add AllChildrenIterator::Seek, r=bz

dom/base/ChildIterator.cpp

@@ -190,7 +190,7 @@ FlattenedChildIterator::Init(bool aIgnoreXBL)
   }
 }
 
-void
+bool
 ExplicitChildIterator::Seek(nsIContent* aChildToFind)
 {
   if (aChildToFind->GetParent() == mParent &&
@@ -204,14 +204,14 @@ ExplicitChildIterator::Seek(nsIContent* aChildToFind)
     mShadowIterator = nullptr;
     mDefaultChild = nullptr;
     mIsFirst = false;
-    return;
+    return true;
   }
 
   // Can we add more fast paths here based on whether the parent of aChildToFind
   // is a shadow insertion point or content insertion point?
 
   // Slow path: just walk all our kids.
-  Seek(aChildToFind, nullptr);
+  return Seek(aChildToFind, nullptr);
 }
 
 nsIContent*
@@ -311,6 +311,37 @@ ExplicitChildIterator::GetPreviousChild()
   return mChild;
 }
 
+bool
+AllChildrenIterator::Seek(nsIContent* aChildToFind)
+{
+  if (mPhase == eNeedBeforeKid) {
+    mPhase = eNeedExplicitKids;
+    nsIFrame* frame = mOriginalContent->GetPrimaryFrame();
+    if (frame) {
+      nsIFrame* beforeFrame = nsLayoutUtils::GetBeforeFrame(frame);
+      if (beforeFrame) {
+        if (beforeFrame->GetContent() == aChildToFind) {
+          return true;
+        }
+      }
+    }
+  }
+
+  if (mPhase == eNeedExplicitKids) {
+    if (ExplicitChildIterator::Seek(aChildToFind)) {
+      return true;
+    }
+    mPhase = eNeedAnonKids;
+  }
+
+  nsIContent* child = nullptr;
+  do {
+    child = GetNextChild();
+  } while (child && child != aChildToFind);
+
+  return child == aChildToFind;
+}
+
 nsIContent*
 AllChildrenIterator::GetNextChild()
 {

dom/base/ChildIterator.h

@@ -64,7 +64,7 @@ public:
   // found.  This version can take shortcuts that the two-argument version
   // can't, so can be faster (and in fact can be O(1) instead of O(N) in many
   // cases).
-  void Seek(nsIContent* aChildToFind);
+  bool Seek(nsIContent* aChildToFind);
 
   // Looks for aChildToFind respecting insertion points until aChildToFind is found.
   // or aBound is found. If aBound is nullptr then the seek is unbounded. Returns
@@ -199,6 +199,8 @@ public:
   ~AllChildrenIterator() { MOZ_ASSERT(!mMutationGuard.Mutated(0)); }
 #endif
 
+  bool Seek(nsIContent* aChildToFind);
+
   nsIContent* GetNextChild();
   nsIContent* Parent() const { return mOriginalContent; }