diff -r 000000000000 -r 6474c204b198 layout/base/DisplayListClipState.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/base/DisplayListClipState.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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/. */
+
+#include "DisplayListClipState.h"
+
+#include "nsDisplayList.h"
+
+namespace mozilla {
+
+const DisplayItemClip*
+DisplayListClipState::GetCurrentCombinedClip(nsDisplayListBuilder* aBuilder)
+{
+  if (mCurrentCombinedClip) {
+    return mCurrentCombinedClip;
+  }
+  if (!mClipContentDescendants && !mClipContainingBlockDescendants) {
+    return nullptr;
+  }
+  if (mClipContentDescendants) {
+    if (mClipContainingBlockDescendants) {
+      DisplayItemClip intersection = *mClipContentDescendants;
+      intersection.IntersectWith(*mClipContainingBlockDescendants);
+      mCurrentCombinedClip = aBuilder->AllocateDisplayItemClip(intersection);
+    } else {
+      mCurrentCombinedClip =
+        aBuilder->AllocateDisplayItemClip(*mClipContentDescendants);
+    }
+  } else {
+    mCurrentCombinedClip =
+      aBuilder->AllocateDisplayItemClip(*mClipContainingBlockDescendants);
+  }
+  return mCurrentCombinedClip;
+}
+
+void
+DisplayListClipState::ClipContainingBlockDescendants(const nsRect& aRect,
+                                                     const nscoord* aRadii,
+                                                     DisplayItemClip& aClipOnStack)
+{
+  if (aRadii) {
+    aClipOnStack.SetTo(aRect, aRadii);
+  } else {
+    aClipOnStack.SetTo(aRect);
+  }
+  if (mClipContainingBlockDescendants) {
+    aClipOnStack.IntersectWith(*mClipContainingBlockDescendants);
+  }
+  mClipContainingBlockDescendants = &aClipOnStack;
+  mCurrentCombinedClip = nullptr;
+}
+
+void
+DisplayListClipState::ClipContentDescendants(const nsRect& aRect,
+                                             const nscoord* aRadii,
+                                             DisplayItemClip& aClipOnStack)
+{
+  if (aRadii) {
+    aClipOnStack.SetTo(aRect, aRadii);
+  } else {
+    aClipOnStack.SetTo(aRect);
+  }
+  if (mClipContentDescendants) {
+    aClipOnStack.IntersectWith(*mClipContentDescendants);
+  }
+  mClipContentDescendants = &aClipOnStack;
+  mCurrentCombinedClip = nullptr;
+}
+
+void
+DisplayListClipState::ClipContainingBlockDescendantsToContentBox(nsDisplayListBuilder* aBuilder,
+                                                                 nsIFrame* aFrame,
+                                                                 DisplayItemClip& aClipOnStack,
+                                                                 uint32_t aFlags)
+{
+  nscoord radii[8];
+  bool hasBorderRadius = aFrame->GetContentBoxBorderRadii(radii);
+  if (!hasBorderRadius && (aFlags & ASSUME_DRAWING_RESTRICTED_TO_CONTENT_RECT)) {
+    return;
+  }
+
+  nsRect clipRect = aFrame->GetContentRectRelativeToSelf() +
+    aBuilder->ToReferenceFrame(aFrame);
+  // If we have a border-radius, we have to clip our content to that
+  // radius.
+  ClipContainingBlockDescendants(clipRect, hasBorderRadius ? radii : nullptr,
+                                 aClipOnStack);
+}
+
+DisplayListClipState::AutoSaveRestore::AutoSaveRestore(nsDisplayListBuilder* aBuilder)
+  : mState(aBuilder->ClipState())
+  , mSavedState(aBuilder->ClipState())
+  , mClipUsed(false)
+  , mRestored(false)
+{}
+
+}