Add a thread-safety assertion in DEFINE_STATIC_LOCAL

Source/platform/WebThreadSupportingGC.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 "config.h"
 #include "platform/WebThreadSupportingGC.h"
 
+#include "wtf/Threading.h"
+
 namespace blink {
 
 PassOwnPtr<WebThreadSupportingGC> WebThreadSupportingGC::create(const char* name)
 {
+#if ENABLE(ASSERT)
+    WTF::willCreateThread();

[kinuko, 2015/01/27 14:50:37]

Adding a hook here feels a bit slippery, suggestions are welcome.

+#endif
     return adoptPtr(new WebThreadSupportingGC(name));
 }
 
 WebThreadSupportingGC::WebThreadSupportingGC(const char* name)
     : m_thread(adoptPtr(Platform::current()->createThread(name)))
 {
 }
 
 WebThreadSupportingGC::~WebThreadSupportingGC()
 {
@@ skipping 16 matching lines @@
 void WebThreadSupportingGC::detachGC()
 {
     ThreadState::current()->removeInterruptor(m_messageLoopInterruptor.get());
     ThreadState::detach();
     platformThread().removeTaskObserver(m_pendingGCRunner.get());
     m_pendingGCRunner = nullptr;
     m_messageLoopInterruptor = nullptr;
 }
 
 } // namespace blink