Add ExitFunnel to prepare for instrumenting browser exits.

components/browser_watcher.gypi

 # Copyright (c) 2014 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.
 
 {
   'conditions': [
   ['OS=="win"', {
       'targets': [
           {
             # This is a separate lib to minimize the dependencies for its
             # hosting binary "chrome_watcher.dll".
             'target_name': 'browser_watcher',
             'type': 'static_library',
             'sources': [
               'browser_watcher/exit_code_watcher_win.cc',
               'browser_watcher/exit_code_watcher_win.h',
             ],
             'dependencies': [
               '../base/base.gyp:base',
             ],
           },
           {
             # Users of the watcher link this target.
             'target_name': 'browser_watcher_client',
             'type': 'static_library',
             'sources': [
+              'browser_watcher/exit_funnel_win.cc',
+              'browser_watcher/exit_funnel_win.h',
               'browser_watcher/watcher_client_win.cc',
               'browser_watcher/watcher_client_win.h',
               'browser_watcher/watcher_main_api_win.cc',
               'browser_watcher/watcher_main_api_win.h',
               'browser_watcher/watcher_metrics_provider_win.cc',
               'browser_watcher/watcher_metrics_provider_win.h',
             ],
             'dependencies': [
               'browser_watcher',
               '../base/base.gyp:base',
             ],
           },
         ],
       }
     ],
   ],
 }