Bug 1180907 - Mutate search label before tinting it. r=sebastian

If we don't mutate, we're tinting the shared Drawable state and other Drawables
using the same asset might also get tinted.

--HG--
extra : commitid : KZghkGnS9ty
extra : rebase_source : f45ac49e5c6c8dcdfa07709ca42b692ef197916e

mobile/android/base/home/SearchEngineBar.java

@@ -175,7 +175,8 @@ public class SearchEngineBar extends TwoWayView
                 view = LayoutInflater.from(getContext()).inflate(R.layout.search_engine_bar_label, parent, false);
             }
 
-            Drawable icon = DrawableCompat.wrap(ContextCompat.getDrawable(parent.getContext(), R.drawable.search_icon_active));
+            final Drawable icon = DrawableCompat.wrap(
+                    ContextCompat.getDrawable(parent.getContext(), R.drawable.search_icon_active).mutate());
             DrawableCompat.setTint(icon, getResources().getColor(R.color.disabled_grey));
 
             final ImageView iconView = (ImageView) view.findViewById(R.id.search_engine_label);