[Sync] Move ModelType and related classes to 'syncer' namespace

sync/syncable/syncable_mock.h

Index: sync/syncable/syncable_mock.h
diff --git a/sync/syncable/syncable_mock.h b/sync/syncable/syncable_mock.h
index c7427925dc90df82ed8fe5bf82a19a49ee2a48df..977f9b35e13c5f46432fd045e0e49b351de28d85 100644
--- a/sync/syncable/syncable_mock.h
+++ b/sync/syncable/syncable_mock.h
@@ -25,12 +25,12 @@ class MockDirectory : public Directory {
 
   MOCK_METHOD1(GetEntryByHandle, syncable::EntryKernel*(int64));
 
-  MOCK_METHOD2(set_last_downloadstamp, void(syncable::ModelType, int64));
+  MOCK_METHOD2(set_last_downloadstamp, void(syncer::ModelType, int64));
 
   MOCK_METHOD1(GetEntryByClientTag,
                syncable::EntryKernel*(const std::string&));
 
-  MOCK_METHOD1(PurgeEntriesWithTypeIn, void(syncable::ModelTypeSet));
+  MOCK_METHOD1(PurgeEntriesWithTypeIn, void(syncer::ModelTypeSet));
 
  private:
   syncer::FakeEncryptor encryptor_;