Move compositor thread input handling logic into content

content/renderer/gpu/render_widget_compositor.h

Index: content/renderer/gpu/render_widget_compositor.h
diff --git a/content/renderer/gpu/render_widget_compositor.h b/content/renderer/gpu/render_widget_compositor.h
index c8c8e0f8789b1dcfdf89e4df2de9bf238c8bd257..feb1515f4b38f67f7f686fc1523f544ac8653383 100644
--- a/content/renderer/gpu/render_widget_compositor.h
+++ b/content/renderer/gpu/render_widget_compositor.h
@@ -5,6 +5,7 @@
 #ifndef CONTENT_RENDERER_GPU_RENDER_WIDGET_COMPOSITOR_H_
 #define CONTENT_RENDERER_GPU_RENDER_WIDGET_COMPOSITOR_H_
 
+#include "base/memory/weak_ptr.h"
 #include "base/time.h"
 #include "cc/debug/rendering_stats.h"
 #include "cc/trees/layer_tree_host_client.h"
@@ -16,6 +17,7 @@
 class SkPicture;
 
 namespace cc {
+class InputHandler;
 class LayerTreeHost;
 struct LatencyInfo;
 }
@@ -32,6 +34,7 @@ class RenderWidgetCompositor : public WebKit::WebLayerTreeView,
 
   virtual ~RenderWidgetCompositor();
 
+  const base::WeakPtr<cc::InputHandler>& GetInputHandler();

[piman, 2013/05/15 21:51:03]

nit: worth mentioning that the weakptr is bound to the impl thread (since this
is called from the main thread).

Do we need this WeakPtr though? It seems redundant with the
InputHandlerClient::WillShutdown.

For startup, assuming we don't call InputHandlerManager::AddInputHandler before
the compositor has been destroyed (from the main thread pov, which has to be the
case given the RenderViewImpl::didActivateCompositor code), then
InputHandlerManager::AddInputHandlerOnCompositorThread will necessarily execute
before ThreadProxy::LayerTreeHostClosedOnImplThread which destroys the
LTHI==InputHandler.

AddInputHandlerOnCompositorThread causes the BindToClient to happen, so you're
guaranteed that by the time LayerTreeHostClosedOnImplThread it will be able to
call WillShutdown (unless, I suppose, the InputHandlerProxy is gone before that,
in which case it doesn't matter any more). At that point you can reset
InputHandlerProxy::input_handler_.

   void SetSuppressScheduleComposite(bool suppress);
   void Animate(base::TimeTicks time);
   void Composite(base::TimeTicks frame_begin_time);
@@ -91,8 +94,6 @@ class RenderWidgetCompositor : public WebKit::WebLayerTreeView,
                                    float page_scale) OVERRIDE;
   virtual scoped_ptr<cc::OutputSurface> CreateOutputSurface() OVERRIDE;
   virtual void DidInitializeOutputSurface(bool success) OVERRIDE;
-  virtual scoped_ptr<cc::InputHandlerClient> CreateInputHandlerClient()
-      OVERRIDE;
   virtual void WillCommit() OVERRIDE;
   virtual void DidCommit() OVERRIDE;
   virtual void DidCommitAndDrawFrame() OVERRIDE;
@@ -103,7 +104,7 @@ class RenderWidgetCompositor : public WebKit::WebLayerTreeView,
   virtual scoped_refptr<cc::ContextProvider>
       OffscreenContextProviderForCompositorThread() OVERRIDE;
 
-private:
+ private:
   explicit RenderWidgetCompositor(RenderWidget* widget);
 
   bool initialize(cc::LayerTreeSettings settings);