Remove 'String::append' from some of the blink source.

Source/core/loader/WorkerThreadableLoader.cpp

Index: Source/core/loader/WorkerThreadableLoader.cpp
diff --git a/Source/core/loader/WorkerThreadableLoader.cpp b/Source/core/loader/WorkerThreadableLoader.cpp
old mode 100644
new mode 100755
index 2cd425fc89c4b90b20ca865bfca725737367c6ac..6960fac2aa77b4a0b6ebd0344d4b0ef9e83881bf
--- a/Source/core/loader/WorkerThreadableLoader.cpp
+++ b/Source/core/loader/WorkerThreadableLoader.cpp
@@ -68,8 +68,7 @@ void WorkerThreadableLoader::loadResourceSynchronously(WorkerGlobalScope* worker
     WorkerRunLoop& runLoop = workerGlobalScope->thread()->runLoop();
 
     // Create a unique mode just for this synchronous resource load.
-    String mode = loadResourceSynchronouslyMode;
-    mode.append(String::number(runLoop.createUniqueId()));
+    String mode = loadResourceSynchronouslyMode + String::number(runLoop.createUniqueId());
 
     RefPtr<WorkerThreadableLoader> loader = WorkerThreadableLoader::create(workerGlobalScope, &client, mode, request, options);
     MessageQueueWaitResult result = MessageQueueMessageReceived;