android: Record the memory size of the GSA process.

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 9a562b9b3b442026c963a302256de0a034ac4060..0e910f7aaa379d712ccc02fb658980ac36c123e1 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -56347,6 +56347,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Search.GsaProcessMemoryPss" units="KB">

[Alexei Svitkine (slow), 2016/11/04 17:25:03]

I feel like it may be better to nest this under Android.* rather than Search.* -
but I'll defer to you to choose.

[Benoit L, 2016/11/07 13:43:11]

This is very closely related to Search.GsaBroadcastsAccountChanges, so I prefer
to keep the naming this way, for more consistency.

+  <owner>lizeb@chromium.org</owner>
+  <summary>
+    On Android, when Chrome connects to a bound service exposed by GSA, the
+    memory footprint of the GSA process in KB, as measured by PSS. Reported at
+    most once per Chrome startup.
+  </summary>
+</histogram>
+
 <histogram name="Search.MigratedPrefToDictionaryValue" enum="BooleanHit">
   <owner>caitkp@chromium.org</owner>
   <summary>