diff -r 000000000000 -r 6474c204b198 mobile/android/base/animation/HeightChangeAnimation.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/animation/HeightChangeAnimation.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,27 @@
+/* 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.animation;
+
+import android.view.View;
+import android.view.animation.Animation;
+import android.view.animation.Transformation;
+
+public class HeightChangeAnimation extends Animation {
+    int mFromHeight;
+    int mToHeight;
+    View mView;
+
+    public HeightChangeAnimation(View view, int fromHeight, int toHeight) {
+        mView = view;
+        mFromHeight = fromHeight;
+        mToHeight = toHeight;
+    }
+
+    @Override
+    protected void applyTransformation(float interpolatedTime, Transformation t) {
+        mView.getLayoutParams().height = Math.round((mFromHeight * (1 - interpolatedTime)) + (mToHeight * interpolatedTime));
+        mView.requestLayout();
+    }
+}