Add a note that user gesture is required to display the media galleries dialog.

R=asargent@chromium.org, vandebo@chromium.org
BUG=None

Review URL: https://chromiumcodereview.appspot.com/17552016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@208049 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/api/media_galleries.idl

@@ -19,7 +19,9 @@ namespace mediaGalleries {
     // before returning the permitted set. Default is silent.  If the value
     // 'yes' is passed, or if the application has not been granted access to
     // any media galleries and the value 'if_needed' is passed, then the
-    // media gallery configuration dialog will be displayed.
+    // media gallery configuration dialog will be displayed. A user
+    // gesture is required for the display of the dialog. (i.e. making the call
+    // in the context of a button press)
     GetMediaFileSystemsInteractivity? interactive;
   };