Support frame tree propagation between renderers in the same browsing instance.

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 45b0c4b1cba7dc1ed302de40d064cbcea5abd60c..8c1e7fad4faf4edd54f1bf150fe78a05dc74040d 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -572,9 +572,16 @@ IPC_STRUCT_BEGIN(ViewMsg_PostMessage_Params)
 
   // When sent to the browser, this is the routing ID of the source frame in
   // the source process.  The browser replaces it with the routing ID of the
-  // equivalent (swapped out) frame in the destination process.  Set to
-  // MSG_ROUTING_NONE if the source frame isn't supported (e.g., subframes).
+  // equivalent (swapped out) frame in the destination process.
   IPC_STRUCT_MEMBER(int, source_routing_id)
+  // The identifier of the source frame in the source process.
+  IPC_STRUCT_MEMBER(int, source_frame_id)
+
+  // The full set of identifiers to uniquely descirbe the target frame. See
+  // the comment on ViewMsg_UpdateFrameTree for details.
+  IPC_STRUCT_MEMBER(int, target_process_id)
+  IPC_STRUCT_MEMBER(int, target_routing_id)
+  IPC_STRUCT_MEMBER(int, target_frame_id)
 
   // The origin of the source frame.
   IPC_STRUCT_MEMBER(string16, source_origin)
@@ -1038,6 +1045,20 @@ IPC_MESSAGE_ROUTED4(ViewMsg_ScriptEvalRequest,
 IPC_MESSAGE_ROUTED1(ViewMsg_PostMessageEvent,
                     ViewMsg_PostMessage_Params)
 
+// Sends a JSON serialized frame tree to render processes along with the
+// process id and route id of the source renderer.
+//
+// When routing JavaScript calls across processes, the destination information
+// is kept in the renderer process instead of the browser process. This design
+// was chosen because frame ids are allocated by the renderer process. If the
+// browser was to keep a mapping of the frame ids across processes, it will
+// require an extra IPC message with the newly allocated frame ids, as a
+// response to this particular message.

[awong, 2012/08/21 19:27:28]

Describe the json format here. Then in other spots that store the string and/or
generate the tree, refer to this comment.

[nasko, 2012/08/21 22:24:13]

The description was in the render view, but I've moved it to the
ViewHostMsg_FrameTreeUpdated, since this is where it all originates.

+IPC_MESSAGE_ROUTED3(ViewMsg_UpdateFrameTree,
+                    int, /* the child process id of the active renderer */
+                    int, /* route_id of the active renderer */
+                    std::string /* json encoded frame tree */)
+
 // Request for the renderer to evaluate an xpath to a frame and insert css
 // into that frame's document. See ViewMsg_ScriptEvalRequest for details on
 // allowed xpath expressions.
@@ -2192,3 +2213,8 @@ IPC_MESSAGE_ROUTED3(ViewHostMsg_PepperPluginHung,
 // Screen was rotated. Dispatched to the onorientationchange javascript API.
 IPC_MESSAGE_ROUTED1(ViewMsg_OrientationChangeEvent,
                     int /* orientation */)
+
+// Sends a JSON serialized frame tree from the active render process to the
+// browser.
+IPC_MESSAGE_ROUTED1(ViewHostMsg_FrameTreeUpdated,
+                    std::string /* json encoded frame tree */)