Smoother scrolling by preparing offscreen tiles (credit: Ben Murdoch)

Change-Id: If8f6aa38174e742e869bce7144de8db84b2f7150

core/java/android/webkit/WebView.java

@@ -8145,6 +8145,15 @@ public class WebView extends AbsoluteLayout
         nativeDraw(canvas, 0, 0, false);
     }
 
+    /**
+     * Enable expanded tiles bound for smoother scrolling.
+     *
+     * @hide only used by the Browser
+     */
+    public void setExpandedTileBounds(boolean enabled) {
+        mWebViewCore.sendMessage(EventHub.SET_EXPANDED_TILE_BOUNDS, enabled ? 1 : 0, 0);
+    }
+
     /**
      * Set the time to wait between passing touches to WebCore. See also the
      * TOUCH_SENT_INTERVAL member for further discussion.

core/java/android/webkit/WebViewCore.java

@@ -578,6 +578,8 @@ final class WebViewCore {
 
     private native void nativeSetJsFlags(String flags);
 
+    private native void nativeSetExpandedTileBounds(boolean enabled);
+
     /**
      *  Delete text from start to end in the focused textfield. If there is no
      *  focus, or if start == end, silently fail.  If start and end are out of
@@ -999,6 +1001,8 @@ final class WebViewCore {
 
         static final int PROXY_CHANGED = 193;
 
+        static final int SET_EXPANDED_TILE_BOUNDS = 194;
+
         // private message ids
         private static final int DESTROY =     200;
 
@@ -1558,6 +1562,10 @@ final class WebViewCore {
                             mWebView.mPrivateHandler.obtainMessage(WebView.AUTOFILL_COMPLETE, null)
                                     .sendToTarget();
                             break;
+
+                        case EventHub.SET_EXPANDED_TILE_BOUNDS:
+                            nativeSetExpandedTileBounds(msg.arg1 == 1);
+                            break;
                     }
                 }
             };