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

content/common/view_messages.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // IPC messages for page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/process.h"
 #include "base/shared_memory.h"
 #include "content/common/content_export.h"
@@ skipping 555 matching lines @@
   IPC_STRUCT_MEMBER(float, scale_factor)
 IPC_STRUCT_END()
 
 IPC_STRUCT_BEGIN(ViewMsg_PostMessage_Params)
   // The serialized script value.
   IPC_STRUCT_MEMBER(string16, data)
 
   // 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).

[Charlie Reis, 2012/08/21 01:40:39]

The "e.g., subframes" part is stale now.  Is there ever a case where we'll set
it to MSG_ROUTING_NONE now?

[nasko, 2012/08/21 17:49:42]

It is still technically possible (in code) to return MSG_ROUTING_NONE, since
FromWebView can return NULL. I'm not sure if there is ever a case where
FromWebView will fail. I've removed the last sentence, but I'd like to
understand the behavior here.

   IPC_STRUCT_MEMBER(int, source_routing_id)
+  IPC_STRUCT_MEMBER(int, source_frame_id)
+
+  IPC_STRUCT_MEMBER(int, remote_process_id)

[Charlie Reis, 2012/08/21 01:40:39]

These need a comment explaining why they're here.  It's not immediately obvious
that the renderer should have this information (without our previous
discussion), rather than just sending up the destination frame ID from the
current renderer process and letting the browser translate it.

Also, perhaps rename them to dest_ instead of remote_ (to be consistent with
source_).

[nasko, 2012/08/21 17:49:42]

Actually, I've added the description to the ViewMsg_UpdateFrameTree IPC message,
since the same set of parameters will likely be present in other JS calls being
routed. I've also made it consistent with the post message parameters and called
it target_ instead of remote_.

+  IPC_STRUCT_MEMBER(int, remote_routing_id)
+  IPC_STRUCT_MEMBER(int, remote_frame_id)
 
   // The origin of the source frame.
   IPC_STRUCT_MEMBER(string16, source_origin)
 
   // The origin for the message's target.
   IPC_STRUCT_MEMBER(string16, target_origin)
 IPC_STRUCT_END()
 
 IPC_STRUCT_BEGIN(ViewHostMsg_DidFailProvisionalLoadWithError_Params)
   // The frame ID for the failure report.
@@ skipping 443 matching lines @@
 IPC_MESSAGE_ROUTED4(ViewMsg_ScriptEvalRequest,
                     string16,  /* frame_xpath */
                     string16,  /* jscript_url */
                     int,  /* ID */
                     bool  /* If true, result is sent back. */)
 
 // Posts a message from a frame in another process to the current renderer.
 IPC_MESSAGE_ROUTED1(ViewMsg_PostMessageEvent,
                     ViewMsg_PostMessage_Params)
 
+// Sends a JSON serialized frame tree to render processes.
+IPC_MESSAGE_ROUTED3(ViewMsg_FrameTree,

[Charlie Reis, 2012/08/21 01:40:39]

Should probably include some kind of verb to make it clear what this is for. 
ViewMsg_UpdateFrameTree?  (This is an instruction from the browser to the
renderer, right?)

[nasko, 2012/08/21 17:49:42]

Done.

+                    int, /* the child process id of the source renderer */

[Charlie Reis, 2012/08/21 01:40:39]

Maybe say "active" instead of "source"?  (I was confusing this with
postMessage's source/dest.)

[nasko, 2012/08/21 17:49:42]

Done.

+                    int, /* route_id of the source 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.
 IPC_MESSAGE_ROUTED2(ViewMsg_CSSInsertRequest,
                     string16,  /* frame_xpath */
                     std::string  /* css string */)
 
 // External popup menus.
 #if defined(OS_MACOSX)
 IPC_MESSAGE_ROUTED1(ViewMsg_SelectPopupMenuItem,
@@ skipping 1134 matching lines @@
 // (according to the value of is_hung). The browser can give the user the
 // option of killing the plugin.
 IPC_MESSAGE_ROUTED3(ViewHostMsg_PepperPluginHung,
                     int /* plugin_child_id */,
                     FilePath /* path */,
                     bool /* is_hung */)
 
 // Screen was rotated. Dispatched to the onorientationchange javascript API.
 IPC_MESSAGE_ROUTED1(ViewMsg_OrientationChangeEvent,
                     int /* orientation */)
+
+// Sends a JSON serialized frame tree from the render process to the browser.
+IPC_MESSAGE_ROUTED1(ViewHostMsg_FrameTree,

[Charlie Reis, 2012/08/21 01:40:39]

As above, ViewHostMsg_FrameTreeUpdated.  Also, maybe mention "from the active
renderer process" so that it's clear swapped out RenderViews won't be sending
this.

[nasko, 2012/08/21 17:49:42]

Done.

+                    std::string /* json encoded frame tree */)