cc: Clean up PictureLayer API.

cc/layers/picture_layer.h

Index: cc/layers/picture_layer.h
diff --git a/cc/layers/picture_layer.h b/cc/layers/picture_layer.h
index 5bafbe5829a83a6dbf2bb4ad78e087f15e21b612..674d35c944644cafd790d383f74463bb33832835 100644
--- a/cc/layers/picture_layer.h
+++ b/cc/layers/picture_layer.h
@@ -37,7 +37,7 @@ class CC_EXPORT PictureLayer : public Layer {
 
   void RunMicroBenchmark(MicroBenchmark* benchmark) override;
 
-  ContentLayerClient* client() { return client_; }
+  ContentLayerClient* client() { return inputs_.client; }
 
   RecordingSource* GetRecordingSourceForTesting() {
     return recording_source_.get();
@@ -63,7 +63,6 @@ class CC_EXPORT PictureLayer : public Layer {
 
   void DropRecordingSourceContentIfInvalid();
 
-  ContentLayerClient* client_;
   std::unique_ptr<RecordingSource> recording_source_;
   devtools_instrumentation::
       ScopedLayerObjectTracker instrumentation_object_tracker_;
@@ -72,7 +71,17 @@ class CC_EXPORT PictureLayer : public Layer {
 
   int update_source_frame_number_;
   bool is_mask_;
-  bool nearest_neighbor_;
+
+  // Encapsulates all data, callbacks or interfaces received from the embedder.
+  struct Inputs {
+    Inputs();
+    ~Inputs();
+
+    ContentLayerClient* client;

[enne (OOO), 2016/07/11 18:00:00]

Can you initialize both of these with default values here? If you don't need a
constructor or destructor, can you remove them?

[Menglin, 2016/07/11 18:12:14]

Done.

+    bool nearest_neighbor;
+  };
+
+  Inputs inputs_;
 
   DISALLOW_COPY_AND_ASSIGN(PictureLayer);
 };