Refactor how surfaces are acquired for GPU compositing.

chrome/browser/gpu_process_host_ui_shim.h

Index: chrome/browser/gpu_process_host_ui_shim.h
diff --git a/chrome/browser/gpu_process_host_ui_shim.h b/chrome/browser/gpu_process_host_ui_shim.h
index 396c2fca8c8cff367199029a3f519817bf91ac33..14c25851362b93f87fba6df544338e25a498b41d 100644
--- a/chrome/browser/gpu_process_host_ui_shim.h
+++ b/chrome/browser/gpu_process_host_ui_shim.h
@@ -11,6 +11,7 @@
 // portion of this class, the GpuProcessHost, is responsible for
 // shuttling messages between the browser and GPU processes.
 
+#include <map>
 #include <queue>
 
 #include "base/callback.h"
@@ -177,6 +178,15 @@ class GpuProcessHostUIShim : public IPC::Channel::Sender,
   std::queue<linked_ptr<CreateCommandBufferCallback> >
       create_command_buffer_requests_;
 
+  typedef std::pair<int32 /* renderer_id */,
+                    int32 /* render_view_id */> ViewID;
+
+  // Encapsulates surfaces that we acquire when creating view command buffers.
+  // We assume that a render view has at most 1 such surface associated
+  // with it.
+  class ViewSurface;
+  std::map<ViewID, linked_ptr<ViewSurface> > acquired_surfaces_;
+
   bool initialized_;
   bool initialized_successfully_;