Added UMA stats to track the budget for any service worker which receives a

chrome/browser/push_messaging/background_budget_service.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 CHROME_BROWSER_PUSH_MESSAGING_BACKGROUND_BUDGET_SERVICE_H_
 #define CHROME_BROWSER_PUSH_MESSAGING_BACKGROUND_BUDGET_SERVICE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 15 matching lines @@
 // worker should be able to do on behalf of the user. The budget is calculated
 // based on the Site Engagment Score and is consumed when a service worker does
 // background work on behalf of the user.
 class BackgroundBudgetService : public KeyedService {
  public:
   explicit BackgroundBudgetService(Profile* profile);
   ~BackgroundBudgetService() override;
 
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);
 
+  // Query for the base cost for any background processing.
+  static double GetBackgroundProcessingCost();
+
   // Get the budget associated with the origin. This is returned as the double
   // budget. Budget will be a value between 0.0 and
   // SiteEngagementScore::kMaxPoints.
   double GetBudget(const GURL& origin);
 
   // Store the budget associated with the origin. Budget should be a value
   // between 0.0 and SiteEngagementScore::kMaxPoints.
   void StoreBudget(const GURL& origin, double budget);
 
  private:
   friend class BackgroundBudgetServiceTest;
 
   // Used to allow tests to fast forward/reverse time.
   void SetClockForTesting(std::unique_ptr<base::Clock> clock);
 
   // The clock used to vend times.
   std::unique_ptr<base::Clock> clock_;
 
   Profile* profile_;
   DISALLOW_COPY_AND_ASSIGN(BackgroundBudgetService);
 };
 
 #endif  // CHROME_BROWSER_PUSH_MESSAGING_BACKGROUND_BUDGET_SERVICE_H_