Add main thread scrolling reasons to GraphicsLayer::layerTreeAsJSON.

ui/compositor/layer.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_COMPOSITOR_LAYER_H_
 #define UI_COMPOSITOR_LAYER_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 354 matching lines @@
   bool PrepareTextureMailbox(
       cc::TextureMailbox* mailbox,
       std::unique_ptr<cc::SingleReleaseCallback>* release_callback,
       bool use_shared_memory) override;
 
   float device_scale_factor() const { return device_scale_factor_; }
 
   // LayerClient
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat> TakeDebugInfo(
       cc::Layer* layer) override;
+  void didUpdateMainThreadScrollingReasons() override;
 
   // Whether this layer has animations waiting to get sent to its cc::Layer.
   bool HasPendingThreadedAnimationsForTesting() const;
 
   // Triggers a call to SwitchToLayer.
   void SwitchCCLayerForTest();
 
   const cc::Region& damaged_region_for_testing() const {
     return damaged_region_;
   }
@@ skipping 144 matching lines @@
   // The texture scale.
   float texture_x_scale_;
   float texture_y_scale_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_H_