Add a switch to emit browser histograms.

base/metrics/statistics_recorder.h

 // Copyright (c) 2012 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.
 
 // StatisticsRecorder holds all Histograms and BucketRanges that are used by
 // Histograms in the system. It provides a general place for
 // Histograms/BucketRanges to register, and supports a global API for accessing
 // (i.e., dumping, or graphing) the data.
 
 #ifndef BASE_METRICS_STATISTICS_RECORDER_H_
@@ skipping 31 matching lines @@
   // histogram (either the argument, or the pre-existing registered histogram).
   static HistogramBase* RegisterOrDeleteDuplicate(HistogramBase* histogram);
 
   // Register, or add a new BucketRanges. If an identically BucketRanges is
   // already registered, then the argument |ranges| will deleted. The returned
   // value is always the registered BucketRanges (either the argument, or the
   // pre-existing one).
   static const BucketRanges* RegisterOrDeleteDuplicateRanges(
       const BucketRanges* ranges);
 
-  // Methods for printing histograms.  Only histograms which have query as
-  // a substring are written to output (an empty string will process all
-  // registered histograms).
+  // Methods for appending histogram data to a string.  Only histograms which
+  // have |query| as a substring are written to |output| (an empty string will
+  // process all registered histograms).
   static void WriteHTMLGraph(const std::string& query, std::string* output);
   static void WriteGraph(const std::string& query, std::string* output);
 
+  // Returns the histograms with |query| as a substring as JSON text.

[Peter Kasting, 2013/11/14 07:04:06]

Nit: Maybe should add "(as in Write[HTML]Graph above, passing an empty string
will return all histograms)"

[grt (UTC plus 2), 2013/11/14 14:44:12]

Done.

+  static std::string ToJSON(const std::string& query);
+
   // Method for extracting histograms which were marked for use by UMA.
   static void GetHistograms(Histograms* output);
 
   // Method for extracting BucketRanges used by all histograms registered.
   static void GetBucketRanges(std::vector<const BucketRanges*>* output);
 
   // Find a histogram by name. It matches the exact name. This method is thread
   // safe.  It returns NULL if a matching histogram is not found.
   static HistogramBase* FindHistogram(const std::string& name);
 
@@ skipping 33 matching lines @@
 
   // Lock protects access to above maps.
   static base::Lock* lock_;
 
   DISALLOW_COPY_AND_ASSIGN(StatisticsRecorder);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_STATISTICS_RECORDER_H_