components: Cleanup class/struct fwd declarations

components/sync/engine_impl/net/server_connection_manager.h

Index: components/sync/engine_impl/net/server_connection_manager.h
diff --git a/components/sync/engine_impl/net/server_connection_manager.h b/components/sync/engine_impl/net/server_connection_manager.h
index b3aee3b917f041212b18302ffbc74547518233f9..9f158233bf83f525bbf97aafcd09958edd380295 100644
--- a/components/sync/engine_impl/net/server_connection_manager.h
+++ b/components/sync/engine_impl/net/server_connection_manager.h
@@ -21,18 +21,10 @@
 #include "components/sync/base/cancelation_observer.h"
 #include "components/sync/syncable/syncable_id.h"
 
-namespace sync_pb {
-class ClientToServerMessage;
-}
-
 namespace syncer {
 
 class CancelationSignal;
 
-namespace syncable {
-class Directory;
-}
-
 static const int32_t kUnsetResponseCode = -1;
 static const int32_t kUnsetContentLength = -1;
 static const int32_t kUnsetPayloadLength = -1;