[BackgroundSync] Track syncManager usage

Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 660 matching lines @@
         CryptoAlgorithmEcdsa = 735,
         CryptoAlgorithmEcdh = 736,
         CryptoAlgorithmHkdf = 737,
         CryptoAlgorithmPbkdf2 = 738,
         DocumentSetDomain = 739,
         UpgradeInsecureRequestsEnabled = 740,
         UpgradeInsecureRequestsUpgradedRequest = 741,
         DocumentDesignMode = 742,
         GlobalCacheStorage = 743,
         NetInfo = 744,
+        BackgroundSync = 745,

[pdr., 2015/03/31 18:46:44]

Small nit: might ServiceWorkerBackgroundSync be a better name? We have various
other background sync mechanisms (though, none web exposed).

[jkarlin, 2015/03/31 18:57:11]

The name clash is indeed unfortunate, but I'm going to stick with BackgroundSync
as it's the terminology used throughout the new code.

 
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.
         // Also, run update_use_counter_feature_enum.py in chromium/src/tools/metrics/histograms/
         // to update the UMA mapping.
         NumberOfFeatures, // This enum value must be last.
     };
 
     // "count" sets the bit for this feature to 1. Repeated calls are ignored.
     static void count(const Frame*, Feature);
@@ skipping 71 matching lines @@
     bool recordMeasurement(Feature feature) { return m_countBits.recordMeasurement(feature); }
     void updateMeasurements();
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h