Add histograms to learn about metrics files dropped for lack of an embedded profile.

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 51751a94b6839889de6c0516e3d72c6b5792f769..e88917ce469c219ebba5f84df5a8fc8a72b7772e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -79016,6 +79016,25 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="UMA.FileMetricsProvider.EmbeddedProfile.DroppedFileAge"
+    units="minutes">
+  <owner>asvitkine@chromium.org</owner>
+  <owner>bcwhite@chromium.org</owner>
+  <summary>
+    Records the last-modified age of a file that was dropped for lack of an
+    embedded profile.
+  </summary>
+</histogram>
+
+<histogram name="UMA.FileMetricsProvider.EmbeddedProfile.DroppedHistogramCount">
+  <owner>asvitkine@chromium.org</owner>
+  <owner>bcwhite@chromium.org</owner>
+  <summary>
+    Records the number of histograms present in a file that was dropped for lack
+    of an embedded profile.
+  </summary>
+</histogram>
+
 <histogram name="UMA.FileMetricsProvider.EmbeddedProfileResult"
     enum="FileMetricsProviderEmbeddedProfileResult">
   <owner>asvitkine@chromium.org</owner>