Add main thread scrolling reasons to GraphicsLayer::layerTreeAsJSON.

third_party/WebKit/Source/platform/scroll/ScrollAnimator.cpp

 /*
  * Copyright (c) 2011, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 367 matching lines @@
         else
             removeMainThreadScrollingReason();
     }
 }
 
 void ScrollAnimator::addMainThreadScrollingReason()
 {
     if (WebLayer* scrollLayer = toWebLayer(getScrollableArea()->layerForScrolling())) {
         scrollLayer->addMainThreadScrollingReasons(
             MainThreadScrollingReason::kAnimatingScrollOnMainThread);
+        getScrollableArea()->layerForScrolling()->debugInfo().setMainThreadScrollingReasons(
+            scrollLayer->mainThreadScrollingReasons());
     }
 }
 
 void ScrollAnimator::removeMainThreadScrollingReason()
 {
     if (WebLayer* scrollLayer = toWebLayer(getScrollableArea()->layerForScrolling())) {
         scrollLayer->clearMainThreadScrollingReasons(
             MainThreadScrollingReason::kAnimatingScrollOnMainThread);
+        getScrollableArea()->layerForScrolling()->debugInfo().setMainThreadScrollingReasons(
+            scrollLayer->mainThreadScrollingReasons());
     }
 }
 
 void ScrollAnimator::notifyCompositorAnimationAborted(int groupId)
 {
     // An animation aborted by the compositor is treated as a finished
     // animation.
     ScrollAnimatorCompositorCoordinator::compositorAnimationFinished(groupId);
 }
 
@@ skipping 53 matching lines @@
     }
     return true;
 }
 
 DEFINE_TRACE(ScrollAnimator)
 {
     ScrollAnimatorBase::trace(visitor);
 }
 
 } // namespace blink