Trigger a full screen repaint when touching layers, as webkitDraw()

may not generate the correct invalidations.

counterpart java CL: https://android-git.corp.google.com/g/#/c/140427/

bug:5425608 bug:5218173
Change-Id: I4a958a6fac4054a1040cb077cdfa2aff076e3fad

core/java/android/webkit/WebViewCore.java

@@ -2019,10 +2019,10 @@ public final class WebViewCore {
         if (nativeUpdateLayers(mLastDrawData.mBaseLayer)) {
             // If anything more complex than position has been touched, let's do a full draw
             webkitDraw();
-        } else {
-            Message.obtain(mWebView.mPrivateHandler,
-                    WebView.INVAL_RECT_MSG_ID).sendToTarget();
         }
+        mWebView.mPrivateHandler.removeMessages(WebView.INVAL_RECT_MSG_ID);
+        mWebView.mPrivateHandler.sendMessageAtFrontOfQueue(mWebView.mPrivateHandler
+                .obtainMessage(WebView.INVAL_RECT_MSG_ID));
     }
 
     private void webkitDraw() {