Add FMP to DataReductionProxy UMA and to Pingback Metrics

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 db79a3ce5c1c80b78b99517e17a4c6ee11bfab69..a4975291ac0f113d89aadb9adb8c832eb832dcd1 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -105656,20 +105656,22 @@ To add a new entry, add it with any value and run test to compute valid value.
   <suffix name="Clients.DataReductionProxy.LoFiOn"
       label="PageLoadMetrics that are a result of a navigation through the
              data reduction proxy with session in LoFi enabled or control
              field trial, and when the connection was slow."/>
   <affected-histogram
       name="PageLoad.DocumentTiming.NavigationToDOMContentLoadedEventFired"/>
   <affected-histogram name="PageLoad.DocumentTiming.NavigationToFirstLayout"/>
   <affected-histogram
       name="PageLoad.DocumentTiming.NavigationToLoadEventFired"/>
   <affected-histogram
+      name="PageLoad.Experimental.PaintTiming.NavigationToFirstMeaningfulPaint"/>
+  <affected-histogram
       name="PageLoad.PaintTiming.NavigationToFirstContentfulPaint"/>
   <affected-histogram name="PageLoad.PaintTiming.NavigationToFirstImagePaint"/>
   <affected-histogram name="PageLoad.PaintTiming.NavigationToFirstPaint"/>
   <affected-histogram name="PageLoad.PaintTiming.NavigationToFirstTextPaint"/>
   <affected-histogram name="PageLoad.ParseTiming.NavigationToParseStart"/>
   <affected-histogram name="PageLoad.ParseTiming.ParseBlockedOnScriptLoad"/>
   <affected-histogram name="PageLoad.ParseTiming.ParseDuration"/>
 </histogram_suffixes>
 
 <histogram_suffixes name="PageLoadMetricsClientsDocWrite" separator="."