Add the ability for the GPU process to be used to paint the backing store of a
tab. This is the first pass and is currently a bit buggy and incomplete.

This patch refactors the backing store to make it a virtual interface which is
then implemented by the platform-specific backing stores. This cleans up the
multi-platform aspects of the old code, and also makes it possible to create
different backing stores (such as ones in another process).

This renames the BackingStore::PaintRect function to PaintToBackingStore which
clears up what it does. I would often get confused and think that it paints
the backing store to the screen.

This makes a common way to capture backing store information and adds it to the
backing store API. This removed a bunch of ugly ifdefs.

This adds the ability for a backing store to specify that the TransportDIB
should not be freed by RenderWidgetHost when painting is complete. This is
necessary since the out-of-process version needs to use it after the
RenderWidget paint function has returned.

This pushes up the vector of copy_rect from RenderWidgetHost to the actual
BackingStores. This prevents us from sending duplicate data over IPC. It also
makes the common non-IPC case more efficient, since we end up setting up various
surfaces only once when there are multiple update rects.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/523028

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@36075 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ipc/ipc_message_utils.h b/ipc/ipc_message_utils.h
index 4f1a6f32..0bffce9a 100644
--- a/ipc/ipc_message_utils.h
+++ b/ipc/ipc_message_utils.h
@@ -48,6 +48,8 @@
   CommandBufferMsgStart,
   UtilityMsgStart,
   UtilityHostMsgStart,
+  GpuMsgStart,
+  GpuHostMsgStart,
   // NOTE: When you add a new message class, also update
   // IPCStatusView::IPCStatusView to ensure logging works.
   LastMsgIndex