PlzNavigate: support NavigationThrottle::WillProcessResponse

content/common/frame_messages.h

 // Copyright 2013 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 interacting with frames.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 861 matching lines @@
 // This message notifies the renderer that the user has closed the find-in-page
 // window (and what action to take regarding the selection).
 IPC_MESSAGE_ROUTED1(FrameMsg_StopFinding, content::StopFindAction /* action */)
 
 #if defined(ENABLE_PLUGINS)
 // Notifies the renderer of updates to the Plugin Power Saver origin whitelist.
 IPC_MESSAGE_ROUTED1(FrameMsg_UpdatePluginContentOriginWhitelist,
                     std::set<url::Origin> /* origin_whitelist */)
 #endif  // defined(ENABLE_PLUGINS)
 
+// Used to instruct the RenderFrame to go into "view source" mode.

[nasko, 2016/03/23 22:16:46]

nit: Add a bit of comment that it is valid to send only for the main frame.

+IPC_MESSAGE_ROUTED0(FrameMsg_EnableViewSourceMode)
+
 // -----------------------------------------------------------------------------
 // Messages sent from the renderer to the browser.
 
 // Blink and JavaScript error messages to log to the console
 // or debugger UI.
 IPC_MESSAGE_ROUTED4(FrameHostMsg_AddMessageToConsole,
                     int32_t,        /* log level */
                     base::string16, /* msg */
                     int32_t,        /* line number */
                     base::string16 /* source id */)
@@ skipping 561 matching lines @@
 IPC_MESSAGE_ROUTED3(FrameHostMsg_FindMatchRects_Reply,
                     int /* version */,
                     std::vector<gfx::RectF> /* rects */,
                     gfx::RectF /* active_rect */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent FrameMsg, then ifdefs for platform specific FrameMsg, then
 // platform independent FrameHostMsg, then ifdefs for platform specific
 // FrameHostMsg.