Add machinery to show touch editing context menus in OOPIFs.

content/common/frame_messages.h

Index: content/common/frame_messages.h
diff --git a/content/common/frame_messages.h b/content/common/frame_messages.h
index ca1ed2d0caf879f42585f15a7b898d60753210cc..688bcfb714c1c7db3ca15c438dc4f148bf16c484 100644
--- a/content/common/frame_messages.h
+++ b/content/common/frame_messages.h
@@ -1039,6 +1039,12 @@ IPC_MESSAGE_ROUTED1(FrameMsg_BlinkFeatureUsageReport,
 IPC_MESSAGE_ROUTED1(FrameMsg_MixedContentFound,
                     FrameMsg_MixedContentFound_Params)
 
+// Sent to inform the renderer to invoke a context menu.
+// The parameter specifies the location in the render view's coordinates.
+IPC_MESSAGE_ROUTED2(FrameMsg_ShowContextMenu,
+                    ui::MenuSourceType,
+                    gfx::Point /* location where menu should be shown */)
+
 // -----------------------------------------------------------------------------
 // Messages sent from the renderer to the browser.