Delete orphaned uma metric MPArch.RWH_DidUpdateBackingStore.

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 51978c4753760570cb02c5835ef16c87b536413c..dcdb93ce41f99d3ef5d58d2cb305bc59f68dbce7 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -1995,7 +1995,6 @@ void RenderWidgetHostImpl::DidUpdateBackingStore(
     const ViewHostMsg_UpdateRect_Params& params,
     const TimeTicks& paint_start) {
   TRACE_EVENT0("renderer_host", "RenderWidgetHostImpl::DidUpdateBackingStore");
-  TimeTicks update_start = TimeTicks::Now();
 
   NotificationService::current()->Notify(
       NOTIFICATION_RENDER_WIDGET_HOST_DID_UPDATE_BACKING_STORE,
@@ -2013,11 +2012,6 @@ void RenderWidgetHostImpl::DidUpdateBackingStore(
       ViewHostMsg_UpdateRect_Flags::is_resize_ack(params.flags);
   if (is_resize_ack)
     WasResized();
-
-  // Log the time delta for processing a paint message.
-  TimeTicks now = TimeTicks::Now();
-  TimeDelta delta = now - update_start;
-  UMA_HISTOGRAM_TIMES("MPArch.RWH_DidUpdateBackingStore", delta);
 }
 
 void RenderWidgetHostImpl::OnQueueSyntheticGesture(