Cleanup redundant namespace usage in Source/platform

Source/platform/scheduler/Scheduler.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef Scheduler_h
 #define Scheduler_h
 
 #include "platform/PlatformExport.h"
 #include "platform/TraceLocation.h"
 #include "wtf/DoubleBufferedDeque.h"
 #include "wtf/Functional.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/ThreadingPrimitives.h"
 
 namespace blink {
-class WebThread;
-}
-
-namespace blink {
 
 // The scheduler is an opinionated gateway for arranging work to be run on the
 // main thread. It decides which tasks get priority over others based on a
 // scheduling policy and the overall system state.
+class WebThread;
+
 class PLATFORM_EXPORT Scheduler {
     WTF_MAKE_NONCOPYABLE(Scheduler);
 public:
     typedef Function<void()> Task;
     // An IdleTask is passed an allotted time in CLOCK_MONOTONIC milliseconds and is expected to complete within this timeframe.
     typedef Function<void(double allottedTimeMs)> IdleTask;
 
     static Scheduler* shared();
     static void initializeOnMainThread();
     static void shutdown();
@@ skipping 57 matching lines @@
     // This mutex protects calls to the pending task queue.
     Mutex m_pendingTasksMutex;
     DoubleBufferedDeque<TracedTask> m_pendingHighPriorityTasks;
 
     volatile int m_highPriorityTaskCount;
 };
 
 } // namespace blink
 
 #endif // Scheduler_h