[Android] Added a flag for the draggable menu button feature.

For more convenient menu item execution, we're planning to do experiment
with draggable menu button. This patch adds a flag to control the feature.
The draggable menu button patch  will land later, after this.

BUG=241613

Review URL: https://chromiumcodereview.appspot.com/15389004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@201949 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 5ec0dad4..aaeb4104 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1454,6 +1454,13 @@
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kSyncfsEnableDirectoryOperation),
   },
+  {
+    "enable-draggable-menu-button",
+    IDS_FLAGS_ENABLE_DRAGGABLE_MENU_BUTTON_NAME,
+    IDS_FLAGS_ENABLE_DRAGGABLE_MENU_BUTTON_DESCRIPTION,
+    kOsAndroid,
+    SINGLE_VALUE_TYPE(switches::kEnableDraggableMenuButton)
+  },
 };
 
 const Experiment* experiments = kExperiments;