[Android]: Hide add-to-homescreen app menu item when WebAPK is installed

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 1494ddb45114dca3faaf518ea1c3a89aa203d64f..6c1aaa9cfb229fd7d3c203e35b7b401d8ce9ec55 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -754,6 +754,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Android.PrepareMenu.OpenWebApkVisibilityCheck" units="ms">
+  <owner>hanxi@chromium.org</owner>
+  <owner>pkotwicz@chromium.org</owner>
+  <summary>
+    Measures the amount of time spent querying for whether a WebAPK is already
+    installed.
+  </summary>
+</histogram>
+
 <histogram name="Android.SeccompStatus.Prctl" enum="AndroidSeccompStatus">
   <owner>rsesek@chromium.org</owner>
   <summary>
@@ -74333,6 +74342,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="WebApk.OpenFromMenu" enum="WebApkOpenResult">
+  <owner>hanxi@chromium.org</owner>
+  <owner>pkotwicz@chromium.org</owner>
+  <summary>
+    When a user visits a PWA for which they have a WebAPK installed, the menu
+    item changes from 'Add to homescreen' to 'Open WebAPK'. This stat tracks
+    whether the opening of the WebAPK was successful when this menu item is

[pkotwicz, 2017/02/24 16:29:40]

Nit: "was successful" -> "is successful"

Either both
"was successful" and "was clicked"
or
"is successful" and "is clicked"

[gonzalon, 2017/02/24 16:41:29]

Done.

+    clicked.
+  </summary>
+</histogram>
+
 <histogram name="WebApk.Update.RequestQueued" enum="WebApkUpdateRequestQueued">
   <owner>hanxi@chromium.org</owner>
   <owner>pkotwicz@chromium.org</owner>
@@ -110815,6 +110835,12 @@ value.
   <int value="1" label="Installation started from the add to homescreen menu"/>
 </enum>
 
+<enum name="WebApkOpenResult" type="int">
+  <int value="0" label="Open an installed WebAPK successfully"/>
+  <int value="1" label="Launch intent for WebAPK is null"/>
+  <int value="2" label="Activity for WebAPK not found."/>
+</enum>
+
 <enum name="WebApkUpdateRequestQueued" type="int">
   <int value="0" label="Queued for the first time"/>
   <int value="1" label="Queued for the second time"/>