Fix Google app crash

Bug: 20110378

Until chromium imlementation lands, use the base implementation.

Change-Id: Icd8e83503770471219718fb38a131938b1bbf0c2

core/java/android/webkit/WebView.java

@@ -2427,7 +2427,9 @@ public class WebView extends AbsoluteLayout
 
     @Override
     public void onProvideVirtualAssistStructure(ViewAssistStructure structure) {
-        mProvider.getViewDelegate().onProvideVirtualAssistStructure(structure);
+        super.onProvideVirtualAssistStructure(structure);
+        // TODO: enable when chromium backend lands.
+        // mProvider.getViewDelegate().onProvideVirtualAssistStructure(structure);
     }
 
     /** @hide */