UMA metrics for measuring first input after first paint renamed.

BUG=479009

Review-Url: https://codereview.chromium.org/2345293002
Cr-Commit-Position: refs/heads/master@{#419252}

chrome/browser/page_load_metrics/observers/core_page_load_metrics_observer.cc

@@ -201,9 +201,9 @@ const char kHistogramFirstMeaningfulPaintStatus[] =
     "PageLoad.Experimental.PaintTiming.FirstMeaningfulPaintStatus";
 
 const char kHistogramFirstNonScrollInputAfterFirstPaint[] =
-    "PageLoad.Input.TimeToFirstNonScroll.AfterPaint";
+    "PageLoad.InputTiming.NavigationToFirstNonScroll.AfterPaint";
 const char kHistogramFirstScrollInputAfterFirstPaint[] =
-    "PageLoad.Input.TimeToFirstScroll.AfterPaint";
+    "PageLoad.InputTiming.NavigationToFirstScroll.AfterPaint";
 
 }  // namespace internal
 

tools/metrics/histograms/histograms.xml

@@ -39587,14 +39587,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram name="PageLoad.Input.TimeToFirstNonScroll.AfterPaint" units="ms">
+<histogram name="PageLoad.InputTiming.NavigationToFirstNonScroll.AfterPaint"
+    units="ms">
   <owner>sahel@chromium.org</owner>
   <summary>
     Measures the time to first non-scroll input after the first paint.
   </summary>
 </histogram>
 
-<histogram name="PageLoad.Input.TimeToFirstScroll.AfterPaint" units="ms">
+<histogram name="PageLoad.InputTiming.NavigationToFirstScroll.AfterPaint"
+    units="ms">
   <owner>sahel@chromium.org</owner>
   <summary>
     Measures the time to first scroll input after the first paint.