Fix removing describe-by for tooltip.

PiperOrigin-RevId: 225254684

Author: TedSander

angular_components/lib/css/material/const/_palette.scss

@@ -10,6 +10,8 @@
 // #############################################################################
 
 // Programmatic access to material colors in SassScript.
+// Inspired by the Angular2 material palettes:
+// https://github.com/angular/angular/blob/master/modules/angular2_material/src/core/style/palette.scss
 
 $mat-red-map: (
   50: $mat-red-50,

angular_components/lib/src/material_tooltip/tooltip_target.dart

@@ -118,6 +118,7 @@ abstract class TooltipBehavior extends TooltipTarget {
   /// of tooltip activate / deactivate.
   @override
   void onClose() {
+    super.onClose();
     hideTooltip(immediate: true);
   }
 }