Let PaintAtAck send an int tag instead of the TransportDIB handle.

chrome/common/render_messages_internal.h

Index: chrome/common/render_messages_internal.h
diff --git a/chrome/common/render_messages_internal.h b/chrome/common/render_messages_internal.h
index f4fb2f64c5bc9b40007afb01c58542b45d128ea4..3ca32ec052318afaa9fe6f59923988ba181c2ccb 100644
--- a/chrome/common/render_messages_internal.h
+++ b/chrome/common/render_messages_internal.h
@@ -153,8 +153,9 @@ IPC_BEGIN_MESSAGES(View)
   // it.  In response to this message, the host generates a
   // ViewHostMsg_PaintAtSize_ACK message.  Note that the DIB *must* be
   // the right size to receive an RGBA image at the |desired_size|.
-  IPC_MESSAGE_ROUTED3(ViewMsg_PaintAtSize,
+  IPC_MESSAGE_ROUTED4(ViewMsg_PaintAtSize,
                       TransportDIB::Handle /* dib_handle */,
+                      int /* tag */,

[brettw at google, 2010/07/19 17:45:23]

Can you add to the comment for this message about what tag is and that it will
be sent back with the ACK?

[Nico, 2010/07/19 18:48:30]

Done.

                       gfx::Size /* page_size */,
                       gfx::Size /* desired_size */)
 
@@ -1125,7 +1126,7 @@ IPC_BEGIN_MESSAGES(ViewHost)
   // Tells the render view that a ViewHostMsg_PaintAtSize message was
   // processed, and the DIB is ready for use.

[brettw at google, 2010/07/19 17:45:23]

Can you add here where tag comes from?

[Nico, 2010/07/19 18:48:30]

Done.

   IPC_MESSAGE_ROUTED2(ViewHostMsg_PaintAtSize_ACK,
-                      TransportDIB::Handle /* dib_handle */,
+                      int /* tag */,
                       gfx::Size /* size */)
 
   // Sent to update part of the view.  In response to this message, the host