[presubmit] Enable readability/namespace linter checking.

src/libplatform/worker-thread.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/libplatform/worker-thread.h"
 
 #include "include/v8-platform.h"
 #include "src/libplatform/task-queue.h"
 
 namespace v8 {
@@ skipping 10 matching lines @@
 }
 
 
 void WorkerThread::Run() {
   while (Task* task = queue_->GetNext()) {
     task->Run();
     delete task;
   }
 }
 
-} }  // namespace v8::platform
+}  // namespace platform
+}  // namespace v8