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

Source/platform/WebThreadSupportingGC.cpp

Index: Source/platform/WebThreadSupportingGC.cpp
diff --git a/Source/platform/WebThreadSupportingGC.cpp b/Source/platform/WebThreadSupportingGC.cpp
index f2aec3e1addf011c63eaf4c1a887c67e01faa58e..549b067b56af1d3990583af1bf8c9959e9250bc5 100644
--- a/Source/platform/WebThreadSupportingGC.cpp
+++ b/Source/platform/WebThreadSupportingGC.cpp
@@ -11,6 +11,29 @@
 
 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)
@@ -35,21 +58,14 @@ WebThreadSupportingGC::~WebThreadSupportingGC()
 
 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