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

chrome/browser/push_messaging/background_budget_service.h

Index: chrome/browser/push_messaging/background_budget_service.h
diff --git a/chrome/browser/push_messaging/background_budget_service.h b/chrome/browser/push_messaging/background_budget_service.h
index 717545a02a6ac464045d7268f625bd42b39610d2..d5daf6e49d586a06d6c42908c6f8ef53ab8c80e7 100644
--- a/chrome/browser/push_messaging/background_budget_service.h
+++ b/chrome/browser/push_messaging/background_budget_service.h
@@ -33,6 +33,9 @@ class BackgroundBudgetService : public KeyedService {
 
   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.