cc: Add LayerTreeHost::InitParams for LayerTreeHost creation.

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index f9667e3d084d3c16922e743e126b2de239488d99..6054b481caad47c1db8dda047c55bda6488f2de0 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -71,26 +71,27 @@ struct ScrollAndScaleSet;
 
 class CC_EXPORT LayerTreeHost {
  public:
+  struct InitParams {
+    LayerTreeHostClient* client = nullptr;
+    SharedBitmapManager* shared_bitmap_manager = nullptr;
+    gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager = nullptr;
+    TaskGraphRunner* task_graph_runner = nullptr;
+    LayerTreeSettings const* settings = nullptr;
+    scoped_refptr<base::SingleThreadTaskRunner> main_task_runner;
+    mutable scoped_ptr<BeginFrameSource> external_begin_frame_source;

[danakj, 2015/05/06 21:00:48]

:( mutable.

this should be a movable type so we can pass/move it by value to LTH instead of
by const&, and then we don't need mutable here.

but in the absence of allowing std::move() how passing it as a (nonconst)
InitParams*, with a TODO to std::move() by value?

[sadrul, 2015/05/06 23:35:43]

Yep, makes sense. Done.

+
+    InitParams();
+    ~InitParams();
+  };
+
   // The SharedBitmapManager will be used on the compositor thread.
   static scoped_ptr<LayerTreeHost> CreateThreaded(
-      LayerTreeHostClient* client,
-      SharedBitmapManager* shared_bitmap_manager,
-      gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager,
-      TaskGraphRunner* task_graph_runner,
-      const LayerTreeSettings& settings,
-      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,
-      scoped_ptr<BeginFrameSource> external_begin_frame_source);
+      const InitParams& params);
 
   static scoped_ptr<LayerTreeHost> CreateSingleThreaded(
-      LayerTreeHostClient* client,
       LayerTreeHostSingleThreadClient* single_thread_client,
-      SharedBitmapManager* shared_bitmap_manager,
-      gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager,
-      TaskGraphRunner* task_graph_runner,
-      const LayerTreeSettings& settings,
-      scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
-      scoped_ptr<BeginFrameSource> external_begin_frame_source);
+      const InitParams& params);
   virtual ~LayerTreeHost();
 
   void SetLayerTreeHostClientReady();
@@ -313,11 +314,7 @@ class CC_EXPORT LayerTreeHost {
   }
 
  protected:
-  LayerTreeHost(LayerTreeHostClient* client,
-                SharedBitmapManager* shared_bitmap_manager,
-                gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager,
-                TaskGraphRunner* task_graph_runner,
-                const LayerTreeSettings& settings);
+  explicit LayerTreeHost(const InitParams& params);
   void InitializeThreaded(
       scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,