[Sync] Refactored ProfileSyncService and remove its backend() function

chrome/browser/sync/glue/autofill_model_associator.h

Index: chrome/browser/sync/glue/autofill_model_associator.h
diff --git a/chrome/browser/sync/glue/autofill_model_associator.h b/chrome/browser/sync/glue/autofill_model_associator.h
index a0eee277ed77802b11e923062fb81b92658de73f..09cfcdc47fd5777ab7742d7be5ced6a649884907 100644
--- a/chrome/browser/sync/glue/autofill_model_associator.h
+++ b/chrome/browser/sync/glue/autofill_model_associator.h
@@ -99,9 +99,6 @@ class AutofillModelAssociator
   // TODO(georgey) : add the same processing for CC info (already in protocol
   // buffers).
 
-  // Returns sync service instance.
-  ProfileSyncService* sync_service() { return sync_service_; }
-
   // Is called to determine if we need to upgrade to the new
   // autofillprofile2 data type. If so we need to sync up autofillprofile
   // first to the latest available changes on the server and then upgrade