Telemetry: Don't silently compare histograms from different processes.

base/metrics/histogram_base.cc

 // 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.
 
 #include "base/metrics/histogram_base.h"
 
 #include <climits>
 
 #include "base/logging.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/pickle.h"
+#include "base/process_util.h"
 #include "base/values.h"
 
 namespace base {
 
 std::string HistogramTypeToString(HistogramType type) {
   switch(type) {
     case HISTOGRAM:
       return "HISTOGRAM";
     case LINEAR_HISTOGRAM:
       return "LINEAR_HISTOGRAM";
@@ skipping 86 matching lines @@
   scoped_ptr<DictionaryValue> parameters(new DictionaryValue());
   GetParameters(parameters.get());
 
   JSONStringValueSerializer serializer(output);
   DictionaryValue root;
   root.SetString("name", histogram_name());
   root.SetInteger("count", count);
   root.SetInteger("flags", flags());
   root.Set("params", parameters.release());
   root.Set("buckets", buckets.release());
+  root.SetInteger("pid", GetCurrentProcId());
   serializer.Serialize(root);
 }
 
 }  // namespace base