Add unit tests for the Background Scheduler.

chrome/android/junit/src/org/chromium/chrome/browser/offlinepages/StubBackgroundSchedulerBridge.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.offlinepages;
+
+import org.chromium.chrome.browser.offlinepages.interfaces.SchedulerBridgeInterface;
+
+/**
+ * Custom stub for our own BackgroundSchedulerBridge.
+ */
+public class StubBackgroundSchedulerBridge implements SchedulerBridgeInterface {
+    private boolean mStartProcessingCalled = false;
+
+    public boolean getStartProcessingCalled() {
+        return mStartProcessingCalled;
+    }
+
+    @Override
+    public boolean startProcessing(
+            SchedulerBridgeInterface.ProcessingDoneCallback callback) {
+        mStartProcessingCalled = true;
+        return true;
+    }
+}