Create and pass shared-histogram-allocator from browser to renderer.

chrome/browser/metrics/chrome_metrics_service_client.cc

Index: chrome/browser/metrics/chrome_metrics_service_client.cc
diff --git a/chrome/browser/metrics/chrome_metrics_service_client.cc b/chrome/browser/metrics/chrome_metrics_service_client.cc
index 4beb0406c600d9932202ea5e11139e8b751033fa..b0c7c3b5d050fe72549eccd21869040a119bed3d 100644
--- a/chrome/browser/metrics/chrome_metrics_service_client.cc
+++ b/chrome/browser/metrics/chrome_metrics_service_client.cc
@@ -23,6 +23,7 @@
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/google/google_brand.h"
 #include "chrome/browser/metrics/chrome_stability_metrics_provider.h"
+#include "chrome/browser/metrics/subprocess_metrics_provider.h"
 #include "chrome/browser/metrics/time_ticks_experiment_win.h"
 #include "chrome/browser/ui/browser_otr_state.h"
 #include "chrome/common/channel_info.h"
@@ -342,6 +343,11 @@ void ChromeMetricsServiceClient::Initialize() {
   metrics_service_.reset(new metrics::MetricsService(
       metrics_state_manager_, this, g_browser_process->local_state()));
 
+  // Gets access to persistent metrics shared by sub-processes.
+  metrics_service_->RegisterMetricsProvider(
+      scoped_ptr<metrics::MetricsProvider>(
+          new metrics::SubprocessMetricsProvider()));
+
   // Register metrics providers.
 #if defined(ENABLE_EXTENSIONS)
   metrics_service_->RegisterMetricsProvider(