Add UMA metrics for window selection and overview.

ash/wm/overview/window_selector.cc

 // Copyright 2013 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 "ash/wm/overview/window_selector.h"
 
 #include <algorithm>
 
 #include "ash/shell.h"
 #include "ash/wm/mru_window_tracker.h"
 #include "ash/wm/overview/window_overview.h"
 #include "ash/wm/overview/window_selector_delegate.h"
 #include "ash/wm/overview/window_selector_panels.h"
 #include "ash/wm/overview/window_selector_window.h"
 #include "ash/wm/window_settings.h"
 #include "base/auto_reset.h"
+#include "base/metrics/histogram.h"
 #include "base/timer/timer.h"
 #include "ui/aura/client/activation_client.h"
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 #include "ui/events/event.h"
 #include "ui/events/event_handler.h"
 
 namespace ash {
 
@@ skipping 98 matching lines @@
         windows_.push_back(panels_item);
       } else {
         panels_item = *iter;
       }
       panels_item->AddWindow(windows[i]);
     } else {
       windows_.push_back(new WindowSelectorWindow(windows[i]));
     }
   }
   RemoveFocusAndSetRestoreWindow();
+  UMA_HISTOGRAM_COUNTS_100("Ash.WindowSelector.Items", windows_.size());
 
   // Observe window activations and switchable containers on all root windows
   // for newly created windows during overview.
   Shell::GetInstance()->activation_client()->AddObserver(this);
   Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
   for (Shell::RootWindowList::const_iterator iter = root_windows.begin();
        iter != root_windows.end(); ++iter) {
     for (size_t i = 0; i < kSwitchableWindowContainerIdsLength; ++i) {
       Shell::GetContainer(*iter,
                           kSwitchableWindowContainerIds[i])->AddObserver(this);
@@ skipping 163 matching lines @@
   // If the window is in the observed_windows_ list it needs to continue to be
   // observed.
   if (observed_windows_.find(restore_focus_window_) ==
           observed_windows_.end()) {
     restore_focus_window_->RemoveObserver(this);
   }
   restore_focus_window_ = NULL;
 }
 
 }  // namespace ash