compositor-worker: Get the thread to run compositor-workers from the Platform.

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 "platform/heap/SafePoint.h"
 #include "public/platform/WebScheduler.h"
 #include "wtf/Threading.h"
 
 namespace blink {
 
+PassOwnPtr<GCSupportForWebThread> GCSupportForWebThread::create(WebThread& thread)
+{
+    return adoptPtr(new GCSupportForWebThread(thread));
+}
+
+GCSupportForWebThread::GCSupportForWebThread(WebThread& thread)
+    : m_thread(thread)
+{
+    m_pendingGCRunner = adoptPtr(new PendingGCRunner);
+    m_thread.addTaskObserver(m_pendingGCRunner.get());
+    ThreadState::attach();
+    OwnPtr<MessageLoopInterruptor> interruptor = adoptPtr(new MessageLoopInterruptor(&m_thread));
+    ThreadState::current()->addInterruptor(interruptor.release());
+}
+
+GCSupportForWebThread::~GCSupportForWebThread()
+{
+    m_thread.removeTaskObserver(m_pendingGCRunner.get());
+
+    ThreadState::detach();
+    m_pendingGCRunner = nullptr;
+}
+
 PassOwnPtr<WebThreadSupportingGC> WebThreadSupportingGC::create(const char* name)
 {
 #if ENABLE(ASSERT)
     WTF::willCreateThread();
 #endif
     return adoptPtr(new WebThreadSupportingGC(name));
 }
 
 WebThreadSupportingGC::WebThreadSupportingGC(const char* name)
     : m_thread(adoptPtr(Platform::current()->createThread(name)))
 {
 }
 
 WebThreadSupportingGC::~WebThreadSupportingGC()
 {
     if (ThreadState::current()) {
         // WebThread's destructor blocks until all the tasks are processed.
         SafePointScope scope(ThreadState::HeapPointersOnStack);
         m_thread.clear();
     }
 }
 
 void WebThreadSupportingGC::initialize()
 {
-    m_pendingGCRunner = adoptPtr(new PendingGCRunner);
-    platformThread().addTaskObserver(m_pendingGCRunner.get());
-    ThreadState::attach();
-    OwnPtr<MessageLoopInterruptor> interruptor = adoptPtr(new MessageLoopInterruptor(&platformThread()));
-    ThreadState::current()->addInterruptor(interruptor.release());
+    m_gcSupport = GCSupportForWebThread::create(platformThread());
 }
 
 void WebThreadSupportingGC::shutdown()
 {
     // Ensure no posted tasks will run from this point on.
-    platformThread().removeTaskObserver(m_pendingGCRunner.get());
     platformThread().scheduler()->shutdown();
-
-    ThreadState::detach();
-    m_pendingGCRunner = nullptr;
+    m_gcSupport.clear();
 }
 
 } // namespace blink