[Sync] Add ClearServerData support to Sync Scheduler

sync/engine/syncer.h

 // Copyright (c) 2012 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.
 
 #ifndef SYNC_ENGINE_SYNCER_H_
 #define SYNC_ENGINE_SYNCER_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 60 matching lines @@
 
   // Requests to download updates for the |request_types|.  For a well-behaved
   // client with a working connection to the invalidations server, this should
   // be unnecessary.  It may be invoked periodically to try to keep the client
   // in sync despite bugs or transient failures.
   // Returns: false if an error occurred and retries should backoff, true
   // otherwise.
   virtual bool PollSyncShare(ModelTypeSet request_types,
                              sessions::SyncSession* session);
 
+  // Posts a ClearServerData command.
+  // Returns: false if an error occurred and retries should backoff, true
+  // otherwise.
+  virtual bool PostClearServerData(sessions::SyncSession* session);
+
  private:
   friend class SyncerTest;
   FRIEND_TEST_ALL_PREFIXES(SyncerTest, NameClashWithResolver);
   FRIEND_TEST_ALL_PREFIXES(SyncerTest, IllegalAndLegalUpdates);
   FRIEND_TEST_ALL_PREFIXES(SyncerTest, TestCommitListOrderingAndNewParent);
   FRIEND_TEST_ALL_PREFIXES(SyncerTest,
                            TestCommitListOrderingAndNewParentAndChild);
   FRIEND_TEST_ALL_PREFIXES(SyncerTest, TestCommitListOrderingCounterexample);
   FRIEND_TEST_ALL_PREFIXES(SyncerTest, TestCommitListOrderingWithNesting);
   FRIEND_TEST_ALL_PREFIXES(SyncerTest, TestCommitListOrderingWithNewItems);
@@ skipping 34 matching lines @@
 
   // Whether the syncer is in the middle of a sync attempt.
   bool is_syncing_;
 
   DISALLOW_COPY_AND_ASSIGN(Syncer);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_SYNCER_H_