Add window overview mode behind --ash-enable-overview-mode flag to F5 key.

chrome/browser/about_flags.cc

 // 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.
 
 #include "chrome/browser/about_flags.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 #include <set>
@@ skipping 1026 matching lines @@
     SINGLE_VALUE_TYPE(switches::kShowLauncherAlignmentMenu)
   },
   {
     "disable-minimize-on-second-launcher-item-click",
     IDS_FLAGS_DISABLE_MINIMIZE_ON_SECOND_LAUNCHER_ITEM_CLICK_NAME,
     IDS_FLAGS_DISABLE_MINIMIZE_ON_SECOND_LAUNCHER_ITEM_CLICK_DESCRIPTION,
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kDisableMinimizeOnSecondLauncherItemClick)
   },
   {
+    "enable-overview-mode",
+    IDS_FLAGS_OVERVIEW_MODE_NAME,
+    IDS_FLAGS_OVERVIEW_MODE_DESCRIPTION,
+    kOsCrOS,
+    SINGLE_VALUE_TYPE(ash::switches::kAshEnableOverviewMode)
+  },
+  {
     "show-touch-hud",
     IDS_FLAGS_SHOW_TOUCH_HUD_NAME,
     IDS_FLAGS_SHOW_TOUCH_HUD_DESCRIPTION,
     kOsAll,
     SINGLE_VALUE_TYPE(ash::switches::kAshTouchHud)
   },
   {
     "enable-pinch",
     IDS_FLAGS_ENABLE_PINCH_SCALE_NAME,
     IDS_FLAGS_ENABLE_PINCH_SCALE_DESCRIPTION,
@@ skipping 1064 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags