Add a histogram for tracking web store promo

chrome/browser/dom_ui/new_tab_ui.h

 // Copyright (c) 2010 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_DOM_UI_NEW_TAB_UI_H_
 #define CHROME_BROWSER_DOM_UI_NEW_TAB_UI_H_
 #pragma once
 
 #include <string>
 
@@ skipping 52 matching lines @@
 
     virtual std::string GetMimeType(const std::string&) const;
 
     // Setters and getters for first_run.
     static void set_first_run(bool first_run) { first_run_ = first_run; }
     static bool first_run() { return first_run_; }
 
    private:
     virtual ~NewTabHTMLSource() {}
 
+    // Records a web store launch in the appropriate histograms. |promo_active|
+    // specifies if the web store promotion was active.
+    void RecordWebStoreLaunch(bool promo_active);
+
+    // Records an app launch in the appropriate histograms. |promo_active|
+    // specifies if the web store promotion was active.
+    void RecordAppLaunch(bool promo_active);
+
+    // Returns true if |path| indicates that the promotion is active, false if
+    // the promo is not active.
+    bool IsPromoActive(const std::string& path);
+
     // Whether this is the first run.
     static bool first_run_;
 
     // Pointer back to the original profile.
     Profile* profile_;
 
     DISALLOW_COPY_AND_ASSIGN(NewTabHTMLSource);
   };
 
  private:
@@ skipping 12 matching lines @@
 
   NotificationRegistrar registrar_;
 
   // The preference version. This used for migrating prefs of the NTP.
   static const int current_pref_version_ = 3;
 
   DISALLOW_COPY_AND_ASSIGN(NewTabUI);
 };
 
 #endif  // CHROME_BROWSER_DOM_UI_NEW_TAB_UI_H_