Move message handlers that don't belong in RenderProcessHostImpl to their own files.

content/content_browser.gypi

 # 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.
 
 {
   'dependencies': [
     'browser/debugger/devtools_resources.gyp:devtools_resources',
     '../base/base.gyp:base_static',
     '../crypto/crypto.gyp:crypto',
     '../net/net.gyp:http_server',
@@ skipping 500 matching lines @@
     'browser/renderer_host/media/media_stream_requester.h',
     'browser/renderer_host/media/media_stream_settings_requester.h',
     'browser/renderer_host/media/video_capture_controller.cc',
     'browser/renderer_host/media/video_capture_controller.h',
     'browser/renderer_host/media/video_capture_controller_event_handler.cc',
     'browser/renderer_host/media/video_capture_controller_event_handler.h',
     'browser/renderer_host/media/video_capture_host.cc',
     'browser/renderer_host/media/video_capture_host.h',
     'browser/renderer_host/media/video_capture_manager.cc',
     'browser/renderer_host/media/video_capture_manager.h',
+    'browser/renderer_host/mhtml_generation_message_filter.cc',
+    'browser/renderer_host/mhtml_generation_message_filter.h',
     'browser/renderer_host/native_web_keyboard_event_android.cc',
     'browser/renderer_host/native_web_keyboard_event_aura.cc',
     'browser/renderer_host/native_web_keyboard_event_gtk.cc',
     'browser/renderer_host/native_web_keyboard_event_mac.mm',
     'browser/renderer_host/native_web_keyboard_event_win.cc',
     'browser/renderer_host/pepper_file_message_filter.cc',
     'browser/renderer_host/pepper_file_message_filter.h',
     'browser/renderer_host/pepper_lookup_request.h',
     'browser/renderer_host/pepper_message_filter.cc',
     'browser/renderer_host/pepper_message_filter.h',
@@ skipping 380 matching lines @@
       ],
     }],
     ['input_speech==0', {
       'sources/': [
         ['exclude', '^browser/speech/'],
       ],
     }],
   ],
 }