Don't drop debug_info when posting to sync server fails

sync/test/engine/mock_connection_manager.h

Index: sync/test/engine/mock_connection_manager.h
diff --git a/sync/test/engine/mock_connection_manager.h b/sync/test/engine/mock_connection_manager.h
index afeaac8a1eab9123d9ab76a4e63460f3e009be9a..6b95eab80161a57f82391988bd36c0aac298eb4d 100644
--- a/sync/test/engine/mock_connection_manager.h
+++ b/sync/test/engine/mock_connection_manager.h
@@ -194,9 +194,10 @@ class MockConnectionManager : public ServerConnectionManager {
   const sync_pb::CommitResponse& last_commit_response() const;
 
   // Retrieve the last request submitted to the server (regardless of type).
-  const sync_pb::ClientToServerMessage& last_request() const {
-    return last_request_;
-  }
+  const sync_pb::ClientToServerMessage& last_request() const;
+
+  // Retrieve the cumulative collection of all requests sent by clients.
+  const std::vector<sync_pb::ClientToServerMessage>& requests() const;
 
   void set_conflict_all_commits(bool value) {
     conflict_all_commits_ = value;
@@ -395,7 +396,7 @@ class MockConnectionManager : public ServerConnectionManager {
 
   std::string next_token_;
 
-  sync_pb::ClientToServerMessage last_request_;
+  std::vector<sync_pb::ClientToServerMessage> requests_;
 
   DISALLOW_COPY_AND_ASSIGN(MockConnectionManager);
 };