LabelButton: Set the label's disabled status to match that of the button

The LabelButton hosts a Label to paints its text content. When the button
is disabled, that Label needs to be disabled as well so that it can paint
itself grayed out.

BUG=155363,162729


Review URL: https://chromiumcodereview.appspot.com/11411358

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171016 0039d316-1c4b-4281-b951-d872f2087c98

ui/views/controls/button/label_button.cc

@@ -153,6 +153,7 @@ void LabelButton::StateChanged() {
   const SkColor color = button_state_colors_[state()];
   if (state() != STATE_DISABLED && label_->enabled_color() != color)
     label_->SetEnabledColor(color);
+  label_->SetEnabled(state() != STATE_DISABLED);
   if (image_->GetPreferredSize() != previous_image_size)
     Layout();
 }