Add main thread scrolling reasons to GraphicsLayer::layerTreeAsJSON.

cc/layers/layer.h

 // Copyright 2010 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 CC_LAYERS_LAYER_H_
 #define CC_LAYERS_LAYER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 323 matching lines @@
   // TODO(chrishtr): Blink no longer resizes anything during paint. We can
   // remove this.
   virtual void SavePaintProperties();
   // Returns true iff anything was updated that needs to be committed.
   virtual bool Update();
   virtual void SetIsMask(bool is_mask) {}
   virtual bool IsSuitableForGpuRasterization() const;
 
   virtual std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
   TakeDebugInfo();
+  virtual void didUpdateMainThreadScrollingReasons();
 
   void SetLayerClient(LayerClient* client) { inputs_.client = client; }
 
   virtual void PushPropertiesTo(LayerImpl* layer);
 
   // Sets the type proto::LayerType that should be used for serialization
   // of the current layer by calling LayerNode::set_type(proto::LayerType).
   // TODO(nyquist): Start using a forward declared enum class when
   // https://github.com/google/protobuf/issues/67 has been fixed and rolled in.
   // This function would preferably instead return a proto::LayerType, but
@@ skipping 364 matching lines @@
   // These all act like draw properties, so don't need push properties.
   gfx::Rect visible_layer_rect_;
   size_t num_unclipped_descendants_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_H_