Support "shared" histograms between processes.

base/metrics/histogram_delta_serialization.cc

 // Copyright 2013 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_delta_serialization.h"
 
 #include "base/logging.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_snapshot_manager.h"
+#include "base/metrics/statistics_recorder.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/pickle.h"
 #include "base/values.h"
 
 namespace base {
 
 namespace {
 
 // Create or find existing histogram and add the samples from pickle.
 // Silently returns when seeing any data problem in the pickle.
@@ skipping 33 matching lines @@
   inconsistent_snapshot_histogram_ =
       Histogram::FactoryGet(
           "Histogram.InconsistentSnapshot" + caller_name, 1, 1000000, 50,
           HistogramBase::kUmaTargetedHistogramFlag);
 }
 
 HistogramDeltaSerialization::~HistogramDeltaSerialization() {
 }
 
 void HistogramDeltaSerialization::PrepareAndSerializeDeltas(
-    std::vector<std::string>* serialized_deltas) {
+    std::vector<std::string>* serialized_deltas,
+    bool include_persistent) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   serialized_deltas_ = serialized_deltas;
   // Note: Before serializing, we set the kIPCSerializationSourceFlag for all
   // the histograms, so that the receiving process can distinguish them from the
   // local histograms.
   histogram_snapshot_manager_.PrepareDeltas(
+      StatisticsRecorder::begin(include_persistent), StatisticsRecorder::end(),
       Histogram::kIPCSerializationSourceFlag, Histogram::kNoFlags);
   serialized_deltas_ = NULL;
 }
 
 // static
 void HistogramDeltaSerialization::DeserializeAndAddSamples(
     const std::vector<std::string>& serialized_deltas) {
   for (std::vector<std::string>::const_iterator it = serialized_deltas.begin();
        it != serialized_deltas.end(); ++it) {
     Pickle pickle(it->data(), checked_cast<int>(it->size()));
@@ skipping 30 matching lines @@
 }
 
 void HistogramDeltaSerialization::InconsistencyDetectedInLoggedCount(
     int amount) {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   inconsistent_snapshot_histogram_->Add(std::abs(amount));
 }
 
 }  // namespace base