[Sync] Move sync/{internal_api,syncable} into syncer namespace

sync/test/null_directory_change_delegate.h

Index: sync/test/null_directory_change_delegate.h
diff --git a/sync/test/null_directory_change_delegate.h b/sync/test/null_directory_change_delegate.h
index 884ae1a9336fc1e79cc52d7160535b9d8f03a1e5..e5b88ffe4a07e3b979fac9716c95aba1e2b9d292 100644
--- a/sync/test/null_directory_change_delegate.h
+++ b/sync/test/null_directory_change_delegate.h
@@ -9,6 +9,7 @@
 #include "base/compiler_specific.h"
 #include "sync/syncable/directory_change_delegate.h"
 
+namespace syncer {
 namespace syncable {
 
 // DirectoryChangeDelegate that does nothing in all delegate methods.
@@ -30,5 +31,6 @@ class NullDirectoryChangeDelegate : public DirectoryChangeDelegate {
 };
 
 }  // namespace syncable
+}  // namespace syncer
 
 #endif  // SYNC_TEST_NULL_DIRECTORY_CHANGE_DELEGATE_H_