Collect metrics on running Accessibility services on Android

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 32ad91d458655d2b7cd4ca0798ac383dc311a918..19b492021597cebc0e8c9b0b859dc1b5769fc0a4 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -78,6 +78,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histograms>
 
+<histogram name="Accessibility.AndroidServiceInfo"
+    enum="AccessibilityAndroidServiceInfoEnum">
+  <owner>dmazzoni@chromium.org</owner>
+  <owner>paulmiller@chromium.org</owner>
+  <summary>
+    Tracks flags and capabilities of enabled accessibility services.

[Mark P, 2017/05/26 18:22:31]

Please state when this is recorded.
https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histo...

It might also help to give guidance on how to interpret this.  For example, it's
clear to me as a metric person that the total number of emits to this histogram
is effectively meaningless.  But that might not be obvious to someone else.

[dmazzoni, 2017/05/31 18:51:37]

Forgot to comment, but I addressed this too, take a look.

+  </summary>
+</histogram>
+
 <histogram name="Accessibility.CrosAlwaysShowA11yMenu" enum="BooleanEnabled">
   <owner>dmazzoni@chromium.org</owner>
   <owner>kenjibaheux@google.com</owner>