Check if a command can be executed before executing it via a shortcut.

Commands are updated when focus is updated. This makes sense, when executing commands by pressing an ui element. However, when executing a command via a shortcut, we may execute it while it shouldn't be allowed to be executed. This patch fixes it by updating the command's state (disabled/enabled) just before executing it via a shortcut.

TEST=Enter Files.app, select a file, then deselect a file, hit Delete button. A delete command should not be invoked.
BUG=174554


Review URL: https://chromiumcodereview.appspot.com/13532006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@192514 0039d316-1c4b-4281-b951-d872f2087c98

ui/webui/resources/js/cr/ui/command.js

@@ -262,6 +262,11 @@ cr.define('cr.ui', function() {
           // We do not want any other element to handle this.
           e.stopPropagation();
 
+          // When invoking a command via a shortcut, we have to manually check
+          // if it can be executed, since focus might not have been changed
+          // what would have updated the command's state.
+          command.canExecuteChange();
+
           command.execute();
           return;
         }