Reduce plugin_metrics_provider_ usage in MetricsService

chrome/browser/metrics/metrics_services_manager.h

Index: chrome/browser/metrics/metrics_services_manager.h
diff --git a/chrome/browser/metrics/metrics_services_manager.h b/chrome/browser/metrics/metrics_services_manager.h
index 538ae6bff8533b57145a16c1d9266ca4344a6476..7f0c51c5519fa4ea06fc7120671e1cee7e38ce11 100644
--- a/chrome/browser/metrics/metrics_services_manager.h
+++ b/chrome/browser/metrics/metrics_services_manager.h
@@ -11,6 +11,7 @@
 #include "chrome/browser/metrics/chrome_metrics_service_client.h"
 
 class MetricsService;
+class PluginMetricsProvider;
 class PrefService;
 
 namespace metrics {
@@ -37,6 +38,9 @@ class MetricsServicesManager {
   // Returns the MetricsService, creating it if it hasn't been created yet.
   MetricsService* GetMetricsService();
 
+  // Returns the PluginMetricsProvider or NULL if plugins aren't enabled.
+  PluginMetricsProvider* GetPluginMetricsProvider();
+
   // Returns the GetRapporService, creating it if it hasn't been created yet.
   rappor::RapporService* GetRapporService();