Record ChromeVox 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 7e94067119120cef98b3dccc797d9749476a9be2..f74b5bb4a4f02481f23c3d3f644262d83c6d03fd 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -113,6 +113,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Accessibility.CrosChromeVoxNext" enum="BooleanEnabled">
+  <owner>dmazzoni@chromium.org</owner>
+  <summary>
+    Set when a Chrome OS user has spoken feedback enabled and is using the next
+    version of ChromeVox.

[Ilya Sherman, 2016/11/15 22:40:32]

Hmm, I'm confused: What is the "next" version?  Next relative to what?  Could
you please expand this description a bit?  Also, please document when precisely
this metric is logged -- is it at browser startup?  When interacting with the
Chrome Vox system?  Something else?

[dmazzoni, 2016/11/16 18:21:25]

"ChromeVox Next" is the name we gave to a new ChromeVox experience
during this period when users can toggle between the old and new
versions. I clarified that in the comment.

+  </summary>
+</histogram>
+
 <histogram name="Accessibility.CrosCursorHighlight" enum="BooleanEnabled">
   <owner>dmazzoni@chromium.org</owner>
   <summary>
@@ -83435,6 +83443,9 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1146" label="LANGUAGESETTINGSPRIVATE_DISABLELANGUAGE"/>
   <int value="1147" label="FILEMANAGERPRIVATEINTERNAL_GETDIRECTORYSIZE"/>
   <int value="1148" label="BLUETOOTHLOWENERGY_SETADVERTISINGINTERVAL"/>
+  <int value="1149" label="ACCESSIBILITY_PRIVATE_RECORDACCESSIBILITYACTION"/>
+  <int value="1150"
+      label="ACCESSIBILITY_PRIVATE_RECORDACCESSIBILITYBOOLEANSTATE"/>
 </enum>
 
 <enum name="ExtensionIconState" type="int">