cc: Clean up PictureLayer API.

cc/layers/picture_layer.h

 // Copyright 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 CC_LAYERS_PICTURE_LAYER_H_
 #define CC_LAYERS_PICTURE_LAYER_H_
 
 #include "base/macros.h"
 #include "cc/base/invalidation_region.h"
 #include "cc/debug/devtools_instrumentation.h"
@@ skipping 19 matching lines @@
   void SetLayerTreeHost(LayerTreeHost* host) override;
   void PushPropertiesTo(LayerImpl* layer) override;
   void SetNeedsDisplayRect(const gfx::Rect& layer_rect) override;
   bool Update() override;
   void SetIsMask(bool is_mask) override;
   sk_sp<SkPicture> GetPicture() const override;
   bool IsSuitableForGpuRasterization() const override;
 
   void RunMicroBenchmark(MicroBenchmark* benchmark) override;
 
-  ContentLayerClient* client() { return client_; }
+  ContentLayerClient* client() { return inputs_.client; }
 
   RecordingSource* GetRecordingSourceForTesting() {
     return recording_source_.get();
   }
 
  protected:
   explicit PictureLayer(ContentLayerClient* client);
   // Allow tests to inject a recording source.
   PictureLayer(ContentLayerClient* client,
                std::unique_ptr<RecordingSource> source);
   ~PictureLayer() override;
 
   bool HasDrawableContent() const override;
   void SetTypeForProtoSerialization(proto::LayerNode* proto) const override;
   void LayerSpecificPropertiesToProto(proto::LayerProperties* proto) override;
   void FromLayerSpecificPropertiesProto(
       const proto::LayerProperties& proto) override;
 
   bool is_mask() const { return is_mask_; }
 
  private:
   friend class TestSerializationPictureLayer;
 
   void DropRecordingSourceContentIfInvalid();
 
-  ContentLayerClient* client_;
   std::unique_ptr<RecordingSource> recording_source_;
   devtools_instrumentation::
       ScopedLayerObjectTracker instrumentation_object_tracker_;
 
   Region last_updated_invalidation_;
 
   int update_source_frame_number_;
   bool is_mask_;
-  bool nearest_neighbor_;
+
+  // Encapsulates all data, callbacks or interfaces received from the embedder.
+  struct Inputs {
+    ContentLayerClient* client;

[enne (OOO), 2016/07/11 18:17:30]

Can you initialize this too to nullptr?

[Menglin, 2016/07/11 18:26:05]

Done.

+    bool nearest_neighbor = false;
+  };
+
+  Inputs inputs_;
 
   DISALLOW_COPY_AND_ASSIGN(PictureLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_PICTURE_LAYER_H_