diff -r 000000000000 -r 6474c204b198 layout/generic/FrameChildList.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/generic/FrameChildList.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,126 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef FrameChildList_h_
+#define FrameChildList_h_
+
+#include "nsFrameList.h"
+#include "nsTArray.h"
+
+class nsIFrame;
+
+namespace mozilla {
+namespace layout {
+
+// enum FrameChildListID lives in nsFrameList.h to solve circular dependencies.
+
+#ifdef DEBUG_FRAME_DUMP
+extern const char* ChildListName(FrameChildListID aListID);
+#endif
+
+class FrameChildListIDs {
+friend class FrameChildListIterator;
+ public:
+  FrameChildListIDs() : mIDs(0) {}
+  FrameChildListIDs(const FrameChildListIDs& aOther) : mIDs(aOther.mIDs) {}
+  FrameChildListIDs(FrameChildListID aListID) : mIDs(aListID) {}
+
+  FrameChildListIDs operator|(FrameChildListIDs aOther) const {
+    return FrameChildListIDs(mIDs | aOther.mIDs);
+  }
+  FrameChildListIDs& operator|=(FrameChildListIDs aOther) {
+    mIDs |= aOther.mIDs;
+    return *this;
+  }
+  bool operator==(FrameChildListIDs aOther) const {
+    return mIDs == aOther.mIDs;
+  }
+  bool operator!=(FrameChildListIDs aOther) const {
+    return !(*this == aOther);
+  }
+  bool Contains(FrameChildListIDs aOther) const {
+    return (mIDs & aOther.mIDs) == aOther.mIDs;
+  }
+
+ protected:
+  FrameChildListIDs(uint32_t aIDs) : mIDs(aIDs) {}
+  uint32_t mIDs;
+};
+
+class FrameChildList {
+ public:
+  FrameChildList(const nsFrameList& aList, FrameChildListID aID)
+    : mList(aList), mID(aID) {}
+  nsFrameList mList;
+  FrameChildListID mID;
+};
+
+/**
+ * A class to iterate frame child lists.
+ */
+class MOZ_STACK_CLASS FrameChildListArrayIterator {
+ public:
+  FrameChildListArrayIterator(const nsTArray<FrameChildList>& aLists)
+    : mLists(aLists), mCurrentIndex(0) {}
+  bool IsDone() const { return mCurrentIndex >= mLists.Length(); }
+  FrameChildListID CurrentID() const {
+    NS_ASSERTION(!IsDone(), "CurrentID(): iterator at end");
+    return mLists[mCurrentIndex].mID;
+  }
+  const nsFrameList& CurrentList() const {
+    NS_ASSERTION(!IsDone(), "CurrentList(): iterator at end");
+    return mLists[mCurrentIndex].mList;
+  }
+  void Next() {
+    NS_ASSERTION(!IsDone(), "Next(): iterator at end");
+    ++mCurrentIndex;
+  }
+
+protected:
+  const nsTArray<FrameChildList>& mLists;
+  uint32_t mCurrentIndex;
+};
+
+/**
+ * A class for retrieving a frame's child lists and iterate them.
+ */
+class MOZ_STACK_CLASS FrameChildListIterator
+  : public FrameChildListArrayIterator {
+ public:
+  FrameChildListIterator(const nsIFrame* aFrame);
+
+protected:
+  nsAutoTArray<FrameChildList,4> mLists;
+};
+
+inline mozilla::layout::FrameChildListIDs
+operator|(mozilla::layout::FrameChildListID aLeftOp,
+          mozilla::layout::FrameChildListID aRightOp)
+{
+  return mozilla::layout::FrameChildListIDs(aLeftOp) |
+         mozilla::layout::FrameChildListIDs(aRightOp);
+}
+
+inline mozilla::layout::FrameChildListIDs
+operator|(mozilla::layout::FrameChildListID aLeftOp,
+          mozilla::layout::FrameChildListIDs aRightOp)
+{
+  return mozilla::layout::FrameChildListIDs(aLeftOp) | aRightOp;
+}
+
+} // namespace layout
+} // namespace mozilla
+
+inline void nsFrameList::AppendIfNonempty(
+         nsTArray<mozilla::layout::FrameChildList>* aLists,
+         mozilla::layout::FrameChildListID aListID) const
+{
+  if (NotEmpty()) {
+    aLists->AppendElement(mozilla::layout::FrameChildList(*this, aListID));
+  }
+}
+
+#endif /* !defined(FrameChildList_h_) */