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

chrome/browser/android/shortcut_info.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ANDROID_SHORTCUT_INFO_H_
 #define CHROME_BROWSER_ANDROID_SHORTCUT_INFO_H_
 
 #include "base/strings/string16.h"
 #include "content/public/common/manifest.h"
 #include "third_party/WebKit/public/platform/modules/screen_orientation/WebScreenOrientationLockType.h"
 #include "url/gurl.h"
 
 // Information needed to create a shortcut via ShortcutHelper.
 struct ShortcutInfo {
+  enum Source {

[Ilya Sherman, 2015/07/03 18:11:45]

Please document that this is used to back an UMA histogram, and therefore should
be treated as append-only.

[dominickn, 2015/07/05 23:33:17]

Done.

+    SOURCE_UNKNOWN = 0,
+    SOURCE_ADD_TO_HOMESCREEN = 1,
+    SOURCE_APP_BANNER = 2,
+    SOURCE_COUNT = 3
+  };
+
   ShortcutInfo();
   explicit ShortcutInfo(const GURL& shortcut_url);
 
   // Updates the info based on the given |manifest|.
   void UpdateFromManifest(const content::Manifest& manifest);
 
+  // Updates the source of the shortcut.
+  void UpdateSource(const Source source);
+
   GURL url;
   base::string16 title;
   content::Manifest::DisplayMode display;
   blink::WebScreenOrientationLockType orientation;
+  Source source;
 };
 
 #endif  // CHROME_BROWSER_ANDROID_SHORTCUT_INFO_H_