Add UMA metrics to track the source of homescreen icons on launch.

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 ea110b9d7b4be2b0f7cfa6091f0e96200de9f0d0..75c285fb4250bad38a798ddd541afc8ffbf6c390 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -14712,6 +14712,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Launch.HomeScreenSource" enum="LaunchFromHomeScreenSource">
+  <owner>dominickn@chromium.org</owner>
+  <summary>
+    Records the source of an Android Home screen shortcut used to launch Chrome.
+  </summary>
+</histogram>
+
 <histogram name="Launch.InvalidIntent" enum="BooleanHit">
   <owner>dfalcantara@chromium.org</owner>
   <summary>
@@ -59447,6 +59454,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Launched as a tab"/>
 </enum>
 
+<enum name="LaunchFromHomeScreenSource" type="int">
+  <int value="0" label="Unknown"/>
+  <int value="1" label="Menu item"/>
+  <int value="2" label="App banner"/>
+</enum>
+
 <enum name="LevelDBCorruptionTypes" type="int">
   <int value="0" label="other"/>
   <int value="1" label="missing files"/>