Introduce RenderProcessHostObserver, use it in its first client.

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/speech/proto/speech_proto.gyp:speech_proto',
     '../base/base.gyp:base_static',
     '../crypto/crypto.gyp:crypto',
     '../google_apis/google_apis.gyp:google_apis',
@@ skipping 130 matching lines @@
     'public/browser/plugin_data_remover.h',
     'public/browser/plugin_service.h',
     'public/browser/plugin_service_filter.h',
     'public/browser/power_save_blocker.h',
     'public/browser/profiler_controller.h',
     'public/browser/profiler_subscriber.h',
     'public/browser/quota_permission_context.h',
     'public/browser/render_frame_host.h',
     'public/browser/render_process_host.h',
     'public/browser/render_process_host_factory.h',
+    'public/browser/render_process_host_observer.h',
     'public/browser/render_view_host.h',
     'public/browser/render_widget_host.h',
     'public/browser/render_widget_host_view.h',
     'public/browser/render_widget_host_view_mac_delegate.h',
     'public/browser/resource_context.h',
     'public/browser/resource_controller.h',
     'public/browser/resource_dispatcher_host.h',
     'public/browser/resource_dispatcher_host_delegate.cc',
     'public/browser/resource_dispatcher_host_delegate.h',
     'public/browser/resource_dispatcher_host_login_delegate.h',
@@ skipping 1444 matching lines @@
         '../build/linux/system.gyp:dbus',
         '../dbus/dbus.gyp:dbus',
       ],
     }, {  # OS != "linux" or use_dbus==0
       'sources!': [
         'browser/geolocation/wifi_data_provider_linux.cc',
       ],
     }],
   ],
 }