[RootLayerScrolls] Annotate non-fast-scroll regions to correct layer

third_party/WebKit/Source/core/paint/PaintLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 29 matching lines @@
  * other provisions required by the MPL or the GPL, as the case may be.
  * If you do not delete the provisions above, a recipient may use your
  * version of this file under any of the LGPL, the MPL or the GPL.
  */
 
 #include "core/paint/PaintLayer.h"
 
 #include "core/CSSPropertyNames.h"
 #include "core/HTMLNames.h"
 #include "core/css/PseudoStyleRequest.h"
+#include "core/dom/ClientRectList.h"
 #include "core/dom/Document.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/FragmentainerIterator.h"
 #include "core/layout/HitTestRequest.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/HitTestingTransformState.h"
 #include "core/layout/LayoutFlowThread.h"
@@ skipping 3131 matching lines @@
     layer = container;
   }
 }
 
 void PaintLayer::clearNeedsRepaintRecursively() {
   for (PaintLayer* child = firstChild(); child; child = child->nextSibling())
     child->clearNeedsRepaintRecursively();
   m_needsRepaint = false;
 }
 
+ClientRectList* PaintLayer::nonFastScrollableRects() const {
+  // This bypasses the isAllowedToQueryCompositingState() check to enabled the
+  // optimization from https://codereview.chromium.org/1256043007
+  CompositedLayerMapping* clm =
+      m_rareData ? m_rareData->compositedLayerMapping.get() : nullptr;
+  if (!clm || !clm->scrollingContentsLayer())
+    return ClientRectList::create();
+  return ClientRectList::create(clm->scrollingContentsLayer()
+                                    ->platformLayer()
+                                    ->nonFastScrollableRegion());
+}
+
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
 void PaintLayer::endShouldKeepAliveAllClientsRecursive() {
   for (PaintLayer* child = firstChild(); child; child = child->nextSibling())
     child->endShouldKeepAliveAllClientsRecursive();
   DisplayItemClient::endShouldKeepAliveAllClients(this);
 }
 #endif
 
 DisableCompositingQueryAsserts::DisableCompositingQueryAsserts()
     : m_disabler(&gCompositingQueryMode, CompositingQueriesAreAllowed) {}
@@ skipping 24 matching lines @@
 }
 
 void showLayerTree(const blink::LayoutObject* layoutObject) {
   if (!layoutObject) {
     LOG(INFO) << "Cannot showLayerTree. Root is (nil)";
     return;
   }
   showLayerTree(layoutObject->enclosingLayer());
 }
 #endif