Support using UMA_HISTOGRAM_CUSTOM_ENUMERATION from the renderer.

base/metrics/histogram.h

 // Copyright (c) 2011 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.
 
 // Histogram is an object that aggregates statistics, and can summarize them in
 // various forms, including ASCII graphical, HTML, and numerically (as a
 // vector of numbers corresponding to each of the aggregating buckets).
 
 // It supports calls to accumulate either time intervals (which are processed
 // as integral number of milliseconds), or arbitrary integral units.
@@ skipping 837 matching lines @@
   //----------------------------------------------------------------------------
   size_t size() const { return ranges_.size(); }
   Histogram::Sample ranges(size_t i) const { return ranges_[i]; }
   void SetBucketRange(size_t i, Histogram::Sample value);
   uint32 range_checksum(uint32 checksum) const { return range_checksum_; }
   void SetRangeChecksum(uint32 checksum) { range_checksum_ = checksum; }
 
   // Return true iff |other| object has same ranges_ as |this| object's ranges_.
   bool Equals(CachedRanges* other) const;
 
+  bool Serialize(Pickle* pickle) const;
+  bool Deserialize(void** iter, const Pickle& pickle);
+
  private:
   // Allow tests to corrupt our innards for testing purposes.
   FRIEND_TEST(HistogramTest, CorruptBucketBounds);
 
   // A monotonically increasing list of values which determine which bucket to
   // put a sample into.  For each index, show the smallest sample that can be
   // added to the corresponding bucket.
   Ranges ranges_;
 
   // Checksum for the conntents of ranges_.  Used to detect random over-writes
   // of our data, and to quickly see if some other CachedRanges instance is
   // possibly Equal() to this instance.
   uint32 range_checksum_;
 
   DISALLOW_COPY_AND_ASSIGN(CachedRanges);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_H_