diff -r 000000000000 -r 6474c204b198 mobile/android/base/gfx/FloatSize.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/gfx/FloatSize.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,54 @@
+/* -*- 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.util.FloatUtils;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+public class FloatSize {
+    public final float width, height;
+
+    public FloatSize(FloatSize size) { width = size.width; height = size.height; }
+    public FloatSize(IntSize size) { width = size.width; height = size.height; }
+    public FloatSize(float aWidth, float aHeight) { width = aWidth; height = aHeight; }
+
+    public FloatSize(JSONObject json) {
+        try {
+            width = (float)json.getDouble("width");
+            height = (float)json.getDouble("height");
+        } catch (JSONException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    @Override
+    public String toString() { return "(" + width + "," + height + ")"; }
+
+    public boolean isPositive() {
+        return (width > 0 && height > 0);
+    }
+
+    public boolean fuzzyEquals(FloatSize size) {
+        return (FloatUtils.fuzzyEquals(size.width, width) &&
+                FloatUtils.fuzzyEquals(size.height, height));
+    }
+
+    public FloatSize scale(float factor) {
+        return new FloatSize(width * factor, height * factor);
+    }
+
+    /*
+     * Returns the size that represents a linear transition between this size and `to` at time `t`,
+     * which is on the scale [0, 1).
+     */
+    public FloatSize interpolate(FloatSize to, float t) {
+        return new FloatSize(FloatUtils.interpolate(width, to.width, t),
+                             FloatUtils.interpolate(height, to.height, t));
+    }
+}
+