Add a histogram for renderer memory usage.

base/metrics/histogram.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.
 
 // 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 199 matching lines @@
 // Support histograming of an enumerated value. Samples should be one of the
 // std::vector<int> list provided via |custom_ranges|. See comments above
 // CustomRanges::FactoryGet about the requirement of |custom_ranges|.
 // You can use the helper function CustomHistogram::ArrayToCustomRanges to
 // transform a C-style array of valid sample values to a std::vector<int>.
 #define HISTOGRAM_CUSTOM_ENUMERATION(name, sample, custom_ranges) \
     STATIC_HISTOGRAM_POINTER_BLOCK(name, Add(sample), \
         base::CustomHistogram::FactoryGet(name, custom_ranges, \
                                           base::HistogramBase::kNoFlags))
 
+#define HISTOGRAM_MEMORY_KB(name, sample) HISTOGRAM_CUSTOM_COUNTS( \
+    name, sample, 1000, 500000, 50)
+
 //------------------------------------------------------------------------------
 // Define Debug vs non-debug flavors of macros.
 #ifndef NDEBUG
 
 #define DHISTOGRAM_TIMES(name, sample) HISTOGRAM_TIMES(name, sample)
 #define DHISTOGRAM_COUNTS(name, sample) HISTOGRAM_COUNTS(name, sample)
 #define DHISTOGRAM_PERCENTAGE(name, under_one_hundred) HISTOGRAM_PERCENTAGE(\
     name, under_one_hundred)
 #define DHISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count) \
     HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count)
@@ skipping 464 matching lines @@
   static bool ValidateCustomRanges(const std::vector<Sample>& custom_ranges);
   static BucketRanges* CreateBucketRangesFromCustomRanges(
       const std::vector<Sample>& custom_ranges);
 
   DISALLOW_COPY_AND_ASSIGN(CustomHistogram);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_HISTOGRAM_H_