Support "shared" histograms between processes.

base/metrics/histogram_delta_serialization.cc

Index: base/metrics/histogram_delta_serialization.cc
diff --git a/base/metrics/histogram_delta_serialization.cc b/base/metrics/histogram_delta_serialization.cc
index f2b825b6d3121c4d8d0fd85f0a49c6df04fe4822..c1746b7c6ad4f397a87045f7240b6a6841675f99 100644
--- a/base/metrics/histogram_delta_serialization.cc
+++ b/base/metrics/histogram_delta_serialization.cc
@@ -7,6 +7,7 @@
 #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"
@@ -60,7 +61,8 @@ 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;
@@ -68,7 +70,10 @@ void HistogramDeltaSerialization::PrepareAndSerializeDeltas(
   // the histograms, so that the receiving process can distinguish them from the
   // local histograms.
   histogram_snapshot_manager_.PrepareDeltas(
-      Histogram::kIPCSerializationSourceFlag, Histogram::kNoFlags);
+      StatisticsRecorder::begin(false),
+      StatisticsRecorder::end(),
+      Histogram::kIPCSerializationSourceFlag,
+      Histogram::kNoFlags);
   serialized_deltas_ = NULL;
 }