WebView animation support

Fix the jumping issue when double tapping

bug:4982054
Change-Id: Ifb67030a3132fe3820a1fcc8ffc97a1ab474c223

Author: Teng-Hui Zhu

core/java/android/webkit/ZoomManager.java

@@ -493,6 +493,9 @@ public void animateZoom(Canvas canvas) {
 
         if (mHardwareAccelerated) {
             mWebView.updateScrollCoordinates(mWebView.getScrollX() - tx, mWebView.getScrollY() - ty);
+            // By adding webView matrix, we need to offset the canvas a bit
+            // to make the animation smooth.
+            canvas.translate(tx, ty);
             setZoomScale(zoomScale, false);
 
             if (mZoomScale == 0) {