Support compositing for active animations in SPv2.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/layout/LayoutInline.h"
@@ skipping 301 matching lines @@
     context.current.renderingContextID = 0;
   }
 }
 
 static CompositingReasons compositingReasonsForTransform(
     const LayoutObject& object) {
   CompositingReasons compositingReasons = CompositingReasonNone;
   if (CompositingReasonFinder::requiresCompositingForTransform(object))
     compositingReasons |= CompositingReason3DTransform;
 
+  if (CompositingReasonFinder::requiresCompositingForAnimation(

[wkorman, 2016/12/15 23:06:00]

Are we not using CompositingReasonFinder::potentialCompositingReasonsFromStyle()
directly just so that we can be thoughtful and integrate these one at a time?

+          object.styleRef()))
+    compositingReasons |= CompositingReasonActiveAnimation;
+
   if (object.styleRef().hasWillChangeCompositingHint() &&
       !object.styleRef().subtreeWillChangeContents())
     compositingReasons |= CompositingReasonWillChangeCompositingHint;
 
   return compositingReasons;
 }
 
 void PaintPropertyTreeBuilder::updateTransform(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
@@ skipping 620 matching lines @@
 #endif
 
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 }
 
 }  // namespace blink