Extract tabbed mode specific logic from the TabPersistenceStore.

chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistencePolicy.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistencePolicy.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistencePolicy.java b/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistencePolicy.java
new file mode 100644
index 0000000000000000000000000000000000000000..aedf958d3533b0eb9b0578be9f15c14d45436813
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tabmodel/TabPersistencePolicy.java
@@ -0,0 +1,99 @@
+// 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.tabmodel;
+
+import org.chromium.base.Callback;
+import org.chromium.chrome.browser.compositor.layouts.content.TabContentManager;
+
+import java.io.File;
+import java.util.List;
+import java.util.concurrent.Executor;
+
+import javax.annotation.Nullable;
+
+/**
+ * Policy that handles the Activity specific behaviors regarding the persistence of tab data.
+ */
+public interface TabPersistencePolicy {
+
+    /**
+     * The prefix of the name of the file where the state is saved.  {@link #getStateFileName()}
+     * and {@link #getStateToBeMergedFileName()} must begin with this prefix.
+     */
+    String SAVED_STATE_FILE_PREFIX = "tab_state";
+
+    /**
+     * @return File representing the directory that is used to store Tab state
+     *         information.
+     */
+    File getOrCreateStateDirectory();
+
+    /**
+     * @return The filename of the primary state file containing information about the tabs to be
+     *         loaded.
+     */
+    String getStateFileName();
+
+    /**
+     * @return The filename of the state that is to be merged.
+     */
+    @Nullable
+    String getStateToBeMergedFileName();
+
+    /**
+     * Performs any necessary migration required before accessing the tab information.
+     *
+     * @param executor The executor that any asynchronous tasks should be run on.
+     * @return Whether any migration is necessary.
+     */
+    boolean performMigration(Executor executor);
+
+    /**
+     * Waits for the task that migrates all state files to their new location to
+     * finish.
+     */
+    void waitForMigrationToFinish();
+
+    /**
+     * @return Whether a merge is currently in progress.
+     */
+    // TODO(tedchoc): Merging is currently very tabbed mode specific.  Investigate moving more
+    //                of the merging logic into this class and out of the main persistence store.
+    boolean isMergeInProgress();
+
+    /**
+     * Marks whether a merge operation has begun or ended.
+     * @param isStarted Whether a merge has been started.
+     */
+    void setMergeInProgress(boolean isStarted);
+
+    /**
+     * Cancels any pending cleanups in progress.
+     */
+    void cancelCleanupInProgress();
+
+    /**
+     * Trigger a clean up for any unused files (both individual state files for tabs as well as
+     * state files for the models).
+     *
+     * @param filesToDelete Callback that is triggered with the filenames to delete.  These files
+     *                      need to reside in {@link #getOrCreateStateDirectory()}.
+     */
+    // TODO(tedchoc): Clean up this API.  This does a mixture of file deletion as well as collecting
+    //                files to be deleted.  It should either handle all deletions internally or not
+    //                do anything but collect files to be deleted.
+    void cleanupUnusedFiles(Callback<List<String>> filesToDelete);
+
+    /**
+     * Sets the {@link TabContentManager} to use.
+     * @param cache The {@link TabContentManager} to use.
+     */
+    void setTabContentManager(TabContentManager cache);
+
+    /**
+     * Notify that persistent store has been destroyed.
+     */
+    void destroy();
+}