Add metrics for YouTube Flash embed rewrite.

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 43a4305fe35f3b6a110edc0990de681c29cde5e9..87a07760b75fe6082be931d2219fbff6556cbfad 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -42469,6 +42469,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Plugin.Flash.YouTubeRewrite" enum="YouTubeRewriteStatus">

[Alexei Svitkine (slow), 2016/08/04 14:31:18]

Have you gotten approval from chrome privacy for this? This is required for
site-specific UMA histograms.

[kdsilva, 2016/08/04 18:28:52]

It will be part of the privacy review. We have details in our design doc here:
https://docs.google.com/document/d/1xHBaX2WhfZVmfeWyLNOX76l9cPiXrQNXqRrUMtlvf...

+  <owner>mlamouri@chromium.org</owner>
+  <owner>kdsilva@google.org</owner>
+  <summary>
+    Records the YouTube Flash embed rewrite status when attempted.
+  </summary>
+</histogram>
+
 <histogram name="Plugin.FlashNavigateUsage" enum="FlashNavigateUsageType">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>Record usage of PPB_Flash.Navigate() Pepper API.</summary>
@@ -95490,6 +95498,13 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1" label="XMLHttpRequestSendArrayBufferView"/>
 </enum>
 
+<enum name="YouTubeRewriteStatus" type="int">
+  <int value="0" label="SUCCESS"/>
+  <int value="1" label="SUCCESS_PARAMS_REWRITE"/>
+  <int value="2" label="SUCCESS_ENABLEJSAPI"/>
+  <int value="3" label="FAILURE_ENABLEJSAPI"/>
+</enum>
+
 </enums>
 
 <!-- Histogram suffixes list -->