Added the Ash.Tab.TimeBetweenSwitchToExistingTabUserActions histogram to track time between tab swit

ash/ash.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
     # These files lists are shared with the GN build.
     'ash_sources': [
       'accelerators/accelerator_commands.cc',
@@ skipping 154 matching lines @@
       'magnifier/magnification_controller.cc',
       'magnifier/magnification_controller.h',
       'magnifier/partial_magnification_controller.cc',
       'magnifier/partial_magnification_controller.h',
       'metrics/task_switch_metrics_recorder.cc',
       'metrics/task_switch_metrics_recorder.h',
       'metrics/task_switch_time_tracker.cc',
       'metrics/task_switch_time_tracker.h',
       'metrics/user_metrics_recorder.cc',
       'metrics/user_metrics_recorder.h',
+      'metrics/user_metrics_recorder_proxy.h',
       'multi_profile_uma.cc',
       'multi_profile_uma.h',
       'networking_config_delegate.cc',
       'networking_config_delegate.h',
       'popup_message.cc',
       'popup_message.h',
       'root_window_controller.cc',
       'root_window_controller.h',
       'root_window_settings.cc',
       'root_window_settings.h',
@@ skipping 1149 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }