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

chrome/browser/android/shortcut_info.cc

Index: chrome/browser/android/shortcut_info.cc
diff --git a/chrome/browser/android/shortcut_info.cc b/chrome/browser/android/shortcut_info.cc
index 24406b889b509c0ea2166e59a1eb8abb2dc9977f..67e0c5549c344667fdc39db4fc854bd8da65ea7d 100644
--- a/chrome/browser/android/shortcut_info.cc
+++ b/chrome/browser/android/shortcut_info.cc
@@ -6,13 +6,15 @@
 
 ShortcutInfo::ShortcutInfo()
     : display(content::Manifest::DISPLAY_MODE_BROWSER),
-      orientation(blink::WebScreenOrientationLockDefault) {
+      orientation(blink::WebScreenOrientationLockDefault),
+      source(SOURCE_ADD_TO_HOMESCREEN) {
 }
 
 ShortcutInfo::ShortcutInfo(const GURL& shortcut_url)
     : url(shortcut_url),
       display(content::Manifest::DISPLAY_MODE_BROWSER),
-      orientation(blink::WebScreenOrientationLockDefault) {
+      orientation(blink::WebScreenOrientationLockDefault),
+      source(SOURCE_ADD_TO_HOMESCREEN) {
 }
 
 void ShortcutInfo::UpdateFromManifest(const content::Manifest& manifest) {
@@ -45,3 +47,7 @@ void ShortcutInfo::UpdateFromManifest(const content::Manifest& manifest) {
       orientation = manifest.orientation;
   }
 }
+
+void ShortcutInfo::UpdateSource(const Source new_source) {
+  source = new_source;
+}