diff -r 000000000000 -r 6474c204b198 mobile/android/base/gfx/PanningPerfAPI.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/gfx/PanningPerfAPI.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,123 @@
+/* -*- 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.RobocopTarget;
+
+import android.os.SystemClock;
+import android.util.Log;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class PanningPerfAPI {
+    private static final String LOGTAG = "GeckoPanningPerfAPI";
+
+    // make this large enough to avoid having to resize the frame time
+    // list, as that may be expensive and impact the thing we're trying
+    // to measure.
+    private static final int EXPECTED_FRAME_COUNT = 2048;
+
+    private static boolean mRecordingFrames = false;
+    private static List<Long> mFrameTimes;
+    private static long mFrameStartTime;
+
+    private static boolean mRecordingCheckerboard = false;
+    private static List<Float> mCheckerboardAmounts;
+    private static long mCheckerboardStartTime;
+
+    private static void initialiseRecordingArrays() {
+        if (mFrameTimes == null) {
+            mFrameTimes = new ArrayList<Long>(EXPECTED_FRAME_COUNT);
+        } else {
+            mFrameTimes.clear();
+        }
+        if (mCheckerboardAmounts == null) {
+            mCheckerboardAmounts = new ArrayList<Float>(EXPECTED_FRAME_COUNT);
+        } else {
+            mCheckerboardAmounts.clear();
+        }
+    }
+
+    @RobocopTarget
+    public static void startFrameTimeRecording() {
+        if (mRecordingFrames || mRecordingCheckerboard) {
+            Log.e(LOGTAG, "Error: startFrameTimeRecording() called while already recording!");
+            return;
+        }
+        mRecordingFrames = true;
+        initialiseRecordingArrays();
+        mFrameStartTime = SystemClock.uptimeMillis();
+    }
+
+    @RobocopTarget
+    public static List<Long> stopFrameTimeRecording() {
+        if (!mRecordingFrames) {
+            Log.e(LOGTAG, "Error: stopFrameTimeRecording() called when not recording!");
+            return null;
+        }
+        mRecordingFrames = false;
+        return mFrameTimes;
+    }
+
+    public static void recordFrameTime() {
+        // this will be called often, so try to make it as quick as possible
+        if (mRecordingFrames) {
+            mFrameTimes.add(SystemClock.uptimeMillis() - mFrameStartTime);
+        }
+    }
+
+    public static boolean isRecordingCheckerboard() {
+        return mRecordingCheckerboard;
+    }
+
+    @RobocopTarget
+    public static void startCheckerboardRecording() {
+        if (mRecordingCheckerboard || mRecordingFrames) {
+            Log.e(LOGTAG, "Error: startCheckerboardRecording() called while already recording!");
+            return;
+        }
+        mRecordingCheckerboard = true;
+        initialiseRecordingArrays();
+        mCheckerboardStartTime = SystemClock.uptimeMillis();
+    }
+
+    @RobocopTarget
+    public static List<Float> stopCheckerboardRecording() {
+        if (!mRecordingCheckerboard) {
+            Log.e(LOGTAG, "Error: stopCheckerboardRecording() called when not recording!");
+            return null;
+        }
+        mRecordingCheckerboard = false;
+
+        // We take the number of values in mCheckerboardAmounts here, as there's
+        // the possibility that this function is called while recordCheckerboard
+        // is still executing. As values are added to this list last, we use
+        // this number as the canonical number of recordings.
+        int values = mCheckerboardAmounts.size();
+
+        // The score will be the sum of all the values in mCheckerboardAmounts,
+        // so weight the checkerboard values by time so that frame-rate and
+        // run-length don't affect score.
+        long lastTime = 0;
+        float totalTime = mFrameTimes.get(values - 1);
+        for (int i = 0; i < values; i++) {
+            long elapsedTime = mFrameTimes.get(i) - lastTime;
+            mCheckerboardAmounts.set(i, mCheckerboardAmounts.get(i) * elapsedTime / totalTime);
+            lastTime += elapsedTime;
+        }
+
+        return mCheckerboardAmounts;
+    }
+
+    public static void recordCheckerboard(float amount) {
+        // this will be called often, so try to make it as quick as possible
+        if (mRecordingCheckerboard) {
+            mFrameTimes.add(SystemClock.uptimeMillis() - mCheckerboardStartTime);
+            mCheckerboardAmounts.add(amount);
+        }
+    }
+}