diff -r 000000000000 -r 6474c204b198 mobile/android/base/gfx/ProgressiveUpdateData.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/gfx/ProgressiveUpdateData.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,33 @@
+/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package org.mozilla.gecko.gfx;
+
+import org.mozilla.gecko.mozglue.generatorannotations.WrapEntireClassForJNI;
+
+/**
+ * This is the data structure that's returned by the progressive tile update
+ * callback function. It encompasses the current viewport and a boolean value
+ * representing whether the front-end is interested in the current progressive
+ * update continuing.
+ */
+@WrapEntireClassForJNI
+public class ProgressiveUpdateData {
+    public float x;
+    public float y;
+    public float width;
+    public float height;
+    public float scale;
+    public boolean abort;
+
+    public void setViewport(ImmutableViewportMetrics viewport) {
+        this.x = viewport.viewportRectLeft;
+        this.y = viewport.viewportRectTop;
+        this.width = viewport.viewportRectRight - this.x;
+        this.height = viewport.viewportRectBottom - this.y;
+        this.scale = viewport.zoomFactor;
+    }
+}
+