Add UMA metric of time to start the first render process

components/startup_metric_utils/browser/startup_metric_utils.h

Index: components/startup_metric_utils/browser/startup_metric_utils.h
diff --git a/components/startup_metric_utils/browser/startup_metric_utils.h b/components/startup_metric_utils/browser/startup_metric_utils.h
index 2e6fd0d3108d662352cd40e69f7760a4dda8e76e..5cf0dda82e4d098345664f3150ca7e14fa43182d 100644
--- a/components/startup_metric_utils/browser/startup_metric_utils.h
+++ b/components/startup_metric_utils/browser/startup_metric_utils.h
@@ -84,7 +84,9 @@ void RecordFirstWebContentsMainFrameLoad(base::TimeTicks ticks);
 
 // Call this with the time when the first web contents had a non-empty paint,
 // only if the first web contents was unimpended in its attempt to do so.

[tdresser, 2017/05/29 13:38:02]

Can we fix unimpended -> unimpeded while we're here?

[hans, 2017/05/31 19:48:57]

Done.

-void RecordFirstWebContentsNonEmptyPaint(base::TimeTicks ticks);
+void RecordFirstWebContentsNonEmptyPaint(
+    base::TimeTicks now,
+    base::TimeTicks render_process_host_init_time);
 
 // Call this with the time when the first web contents began navigating its main
 // frame. Adds a suffix to its metrics according to |workload|.