Add "Search" key press/hold UMA metrics.

ash/common/accelerators/accelerator_router.h

 // Copyright 2016 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.
 
 #ifndef ASH_ACCELERATORS_ACCELERATOR_ROUTER_H_
 #define ASH_ACCELERATORS_ACCELERATOR_ROUTER_H_
 
 #include "ash/ash_export.h"
 #include "base/macros.h"
+#include "base/time/time.h"
 
 namespace ui {
 class Accelerator;
 class KeyEvent;
 }
 
 namespace ash {
 
 class WmWindow;
 
@@ skipping 14 matching lines @@
  private:
   // Returns true if the window should be allowed a chance to handle
   // system keys.
   bool CanConsumeSystemKeys(WmWindow* target, const ui::KeyEvent& event);
 
   // Returns true if the |accelerator| should be processed now.
   bool ShouldProcessAcceleratorNow(WmWindow* target,
                                    const ui::KeyEvent& event,
                                    const ui::Accelerator& accelerator);
 
+  // Records a histogram on how long the "Search" key is held when a user
+  // presses an accelerator that involes the "Search" key.
+  void RecordSearchKeyStats(const ui::Accelerator& accelerator);
+
+  enum SearchKeyState { RELEASED = 0, PRESSED, RECORDED };
+  SearchKeyState search_key_state_ = RELEASED;
+  base::TimeTicks search_key_pressed_timestamp_;
+
   DISALLOW_COPY_AND_ASSIGN(AcceleratorRouter);
 };
 
 }  // namespace ash
 
 #endif  // ASH_ACCELERATORS_ACCELERATOR_ROUTER_H_