[Offline pages] Adding capability to free up space used by Offline pages

chrome/android/java/src/org/chromium/chrome/browser/offline_pages/OfflinePageFreeUpSpaceCallback.java

+// Copyright 2015 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.offline_pages;
+
+/** Interface for informing the caller that the clean up operation is completed. */
+public interface OfflinePageFreeUpSpaceCallback {
+    /** Called when clean up operation is completed. */
+    void onFreeUpSpaceDone();
+
+    /** Called when clean up operation is canceled. */
+    void onFreeUpSpaceCancelled();
+}