Rewrite references to "wtf/" to "platform/wtf/" in the rest of platform/.

third_party/WebKit/Source/platform/WebThread.cpp

 // 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.
 
 #include "public/platform/WebThread.h"
 
 #include "platform/WebTaskRunner.h"
-#include "wtf/Assertions.h"
+#include "platform/wtf/Assertions.h"
 
 #if OS(WIN)
 #include <windows.h>
 #elif OS(POSIX)
 #include <unistd.h>
 #endif
 
 namespace blink {
 
 #if OS(WIN)
 static_assert(sizeof(blink::PlatformThreadId) >= sizeof(DWORD),
               "size of platform thread id is too small");
 #elif OS(POSIX)
 static_assert(sizeof(blink::PlatformThreadId) >= sizeof(pid_t),
               "size of platform thread id is too small");
 #else
 #error Unexpected platform
 #endif
 
 base::SingleThreadTaskRunner* WebThread::GetSingleThreadTaskRunner() {
   return GetWebTaskRunner()->ToSingleThreadTaskRunner();
 }
 
 }  // namespace blink