Added UMA metrics for ChromeOS first-run UI.

chrome/browser/chromeos/first_run/step.h

 // 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_FIRST_RUN_STEP_H_
 #define CHROME_BROWSER_CHROMEOS_FIRST_RUN_STEP_H_
 
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/time/time.h"
 
 namespace ash {
 class FirstRunHelper;
 }
 
 namespace gfx {
 class Size;
 }
 
 namespace chromeos {
 
 class FirstRunActor;
 
 namespace first_run {
 
 class Step {
  public:
   Step(const std::string& name,
        ash::FirstRunHelper* shell_helper,
        FirstRunActor* actor);
   virtual ~Step();
 
   // Step shows its content.
-  virtual void Show() = 0;
+  void Show();
 
-  // Called before hiding step. Default implementation removes holes from
-  // background.
-  virtual void OnBeforeHide();
+  // Called before hiding step.
+  void OnBeforeHide();
 
   // Called after step has been hidden.
-  virtual void OnAfterHide();
-
-  // Returns size of overlay window.
-  gfx::Size GetOverlaySize() const;
+  void OnAfterHide();
 
   const std::string& name() const { return name_; }
 
  protected:
   ash::FirstRunHelper* shell_helper() const { return shell_helper_; }
   FirstRunActor* actor() const { return actor_; }
+  gfx::Size GetOverlaySize() const;
+
+  // Called from Show method.
+  virtual void DoShow() = 0;
+
+  // Called from OnBeforeHide. Step implementation could override this method to
+  // react on corresponding event.
+  virtual void DoOnBeforeHide() {}
+
+  // Called from OnAfterHide. Step implementation could override this method to
+  // react on event.
+  virtual void DoOnAfterHide() {}
 
  private:
+  // Records time spent on step to UMA.
+  void RecordCompletion();
+
   std::string name_;
   ash::FirstRunHelper* shell_helper_;
   FirstRunActor* actor_;
+  base::Time show_time_;
 
   DISALLOW_COPY_AND_ASSIGN(Step);
 };
 
 }  // namespace first_run
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FIRST_RUN_STEP_H_