Add UMA metrics regarding default browser status

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 456f2a74f31cb810d4be4b8eb043c964e295f932..6de6699c82fbdc24dbb5438d8eb706d5b2567e44 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -30330,6 +30330,29 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Mobile.DefaultBrowser.BrowserCount.ChromeDefault">

[Ilya Sherman, 2017/04/28 21:14:30]

Please use a histogram_suffixes element to avoid repeating the docs for this
histogram; and please add a brief label for each suffix, so that it's extra
clear what the histogram is measuring.

[David Trainor- moved to gerrit, 2017/05/03 21:51:13]

Done.

+  <owner>dtrainor@chromium.org</owner>
+  <summary>Android: The number of browsers installed on the device.</summary>
+</histogram>
+
+<histogram name="Mobile.DefaultBrowser.BrowserCount.NoDefault">
+  <owner>dtrainor@chromium.org</owner>
+  <summary>Android: The number of browsers installed on the device.</summary>
+</histogram>
+
+<histogram name="Mobile.DefaultBrowser.BrowserCount.OtherDefault">
+  <owner>dtrainor@chromium.org</owner>
+  <summary>Android: The number of browsers installed on the device.</summary>
+</histogram>
+
+<histogram name="Mobile.DefaultBrowser.State" enum="MobileDefaultBrowserState">
+  <owner>dtrainor@chromium.org</owner>
+  <summary>
+    Android: Whether or not the device has a default browser and whether or not
+    it is a system installed browser.
+  </summary>
+</histogram>
+
 <histogram name="Mobile.SystemNotification.Blocked"
     enum="SystemNotificationType">
   <owner>dtrainor@chromium.org</owner>
@@ -105679,6 +105702,14 @@ from previous Chrome versions.
   <int value="1" label="Failure"/>
 </enum>
 
+<enum name="MobileDefaultBrowserState" type="int">
+  <int value="0" label="No default"/>
+  <int value="1" label="Chrome: System default"/>
+  <int value="2" label="Chrome: Installed default"/>
+  <int value="3" label="Other: System default"/>
+  <int value="4" label="Other: Installed default"/>
+</enum>
+
 <enum name="MobileDownloadCancelReason" type="int">
   <int value="0" label="Not canceled"/>
   <int value="1" label="Click on the cancel button"/>