Add zoom extension API

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 dada88c3bd61d644cf347a9a91d446c57a98d202..193d0fcdb7f63833b83827aa08122d331275e0f6 100644
--- a/chrome/common/render_messages_internal.h
+++ b/chrome/common/render_messages_internal.h
@@ -424,7 +424,8 @@ IPC_MESSAGE_ROUTED1(ViewMsg_Zoom,
 // Set the zoom level for the current main frame.  If the level actually
 // changes, a ViewHostMsg_DidZoomURL message will be sent back to the browser
 // telling it what url got zoomed and what its current zoom level is.
-IPC_MESSAGE_ROUTED1(ViewMsg_SetZoomLevel,
+IPC_MESSAGE_ROUTED2(ViewMsg_SetZoomLevel,
+                    int /* request_id */,
                     double /* zoom_level */)
 
 // Set the zoom level for a particular url that the renderer is in the
@@ -1879,7 +1880,8 @@ IPC_MESSAGE_ROUTED1(ViewHostMsg_UploadProgress_ACK,
 // browser can update its records.  If remember is true, then url is used to
 // update the zoom level for all pages in that site.  Otherwise, the render
 // view's id is used so that only the menu is updated.
-IPC_MESSAGE_ROUTED3(ViewHostMsg_DidZoomURL,
+IPC_MESSAGE_ROUTED4(ViewHostMsg_DidZoomURL,
+                    int /* request_id */,
                     double /* zoom_level */,
                     bool /* remember */,
                     GURL /* url */)