Add Foreground-to-FirstMeaningfulPaint histogram

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index e5c5bcc50d590ae8891545f79ac665dc147bc39c..b5fd277a8cb7898ed4962c9080cc302186699b6c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -49281,6 +49281,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram
+    name="PageLoad.Experimental.PaintTiming.ForegroundToFirstMeaningfulPaint"
+    units="ms">
+  <owner>ksakamoto@chromium.org</owner>
+  <summary>
+    Measures the time from a background tab being switched to the foreground to
+    the time the first meaningful paint is performed, for main frame documents.
+  </summary>
+</histogram>
+
 <histogram
     name="PageLoad.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint"
     units="ms">
@@ -49568,6 +49578,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="PageLoad.PaintTiming.ForegroundToFirstContentfulPaint"
+    units="ms">
+  <owner>ksakamoto@chromium.org</owner>
+  <summary>
+    Measures the time from a background tab being switched to the foreground to
+    the time the first contentful paint is performed, for main frame documents.
+  </summary>
+</histogram>
+
 <histogram name="PageLoad.PaintTiming.ForegroundToFirstPaint" units="ms">
   <owner>pkotwicz@chromium.org</owner>
   <summary>