sync: Add GetAllSyncData to sync/api

chrome/browser/extensions/extension_service_unittest.cc

Index: chrome/browser/extensions/extension_service_unittest.cc
diff --git a/chrome/browser/extensions/extension_service_unittest.cc b/chrome/browser/extensions/extension_service_unittest.cc
index c0ebbc5929c299500c4d08c918b0c5f1c2ce54c8..232ce60586ee0b959a75bb86528fbebff2f308cb 100644
--- a/chrome/browser/extensions/extension_service_unittest.cc
+++ b/chrome/browser/extensions/extension_service_unittest.cc
@@ -5090,6 +5090,11 @@ namespace {
         const syncer::SyncChangeList& change_list) OVERRIDE {
       return syncer::SyncError();
     }
+
+    virtual syncer::SyncDataList GetAllSyncData(
+        syncer::ModelType type) const {
+      return syncer::SyncDataList();
+    }
   };
 }