Revert of 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 1d7717722a8a5488b91024b5d229762302ffcfdf..6e16b162bca16cb5cddce4580eb04d973c7892cc 100644
--- a/chrome/browser/metrics/metrics_services_manager.h
+++ b/chrome/browser/metrics/metrics_services_manager.h
@@ -12,10 +12,6 @@
 class ChromeMetricsServiceClient;
 class MetricsService;
 class PrefService;
-
-namespace base {
-class FilePath;
-}
 
 namespace metrics {
 class MetricsStateManager;
@@ -47,9 +43,6 @@
   // Returns the VariationsService, creating it if it hasn't been created yet.
   chrome_variations::VariationsService* GetVariationsService();
 
-  // Should be called when a plugin loading error occurs.
-  void OnPluginLoadingError(const base::FilePath& plugin_path);
-
  private:
   metrics::MetricsStateManager* GetMetricsStateManager();