Adds logging metrics to translate infobar.

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 32f6e0504d0c1cdb42bd07cd008ccbc75effa6c5..ff2e165c742c115375f85fcee6ff6451375f0c26 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -75747,6 +75747,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Translate.CompactInfobar.Count">

[Ilya Sherman, 2017/05/15 22:59:53]

nit: "Foo.Count" reads about the same as "Foo" for a histogram -- all histograms
are counts.  Please update this name to clarify what's being counted -- e.g.
"TranslationsPerPage".

[ramyasharma, 2017/05/16 05:40:10]

Thanks Done.

+  <owner>ramyasharma@google.com</owner>
+  <summary>Records the total number of times a page was translated.</summary>

[Ilya Sherman, 2017/05/15 22:59:53]

This is not quite detailed enough.  Could you please document when this is
recorded?  Also, it's not clear to me why a page might be translated multiple
times -- is that a bug?  It might be helpful to provide a motivating example for
why a page might undergo multiple translations.

[ramyasharma, 2017/05/16 05:40:10]

This is not a bug, its a feature. User has the flexibility to pick any number of
target languages and translate. Not many users will obviously translate to more
than one language, but this is what we want to measure. 
Also reverting back to the original language counts as 1 translation.

+</histogram>
+
 <histogram name="Translate.CompactInfobar.Event" enum="TranslateCompactUIEvent">
   <owner>ramyasharma@google.com</owner>
   <summary>Various user actions performed in the translate infobar.</summary>