compositor-worker: Share a thread and an isolate for compositor workers.

Source/modules/compositorworker/CompositorWorkerThread.cpp

Index: Source/modules/compositorworker/CompositorWorkerThread.cpp
diff --git a/Source/modules/compositorworker/CompositorWorkerThread.cpp b/Source/modules/compositorworker/CompositorWorkerThread.cpp
index b540dd5befbdaaef56f553d9d110a4dcbc5435b0..3da1f9996a15a537f1eb0c7b54c0ea08cc2480c8 100644
--- a/Source/modules/compositorworker/CompositorWorkerThread.cpp
+++ b/Source/modules/compositorworker/CompositorWorkerThread.cpp
@@ -8,7 +8,9 @@
 #include "bindings/core/v8/V8Initializer.h"
 #include "core/workers/WorkerObjectProxy.h"
 #include "core/workers/WorkerThreadStartupData.h"
+#include "core/workers/WorkerV8Isolate.h"
 #include "modules/compositorworker/CompositorWorkerGlobalScope.h"
+#include "modules/compositorworker/CompositorWorkerManager.h"
 #include "public/platform/Platform.h"
 
 namespace blink {
@@ -38,8 +40,27 @@ PassRefPtrWillBeRawPtr<WorkerGlobalScope> CompositorWorkerThread::createWorkerGl
 WebThreadSupportingGC& CompositorWorkerThread::backingThread()
 {
     if (!m_thread)
-        m_thread = WebThreadSupportingGC::create("CompositorWorker Thread");
-    return *m_thread.get();
+        m_thread = &CompositorWorkerManager::instance()->compositorWorkerThread();
+    return *m_thread;
+}
+
+void CompositorWorkerThread::initializeBackingThread()
+{
+    CompositorWorkerManager::instance()->initializeBackingThread();
+}
+
+void CompositorWorkerThread::shutdownBackingThread()
+{
+    CompositorWorkerManager::instance()->shutdownBackingThread();
+}
+
+OwnPtr<WorkerV8Isolate>& CompositorWorkerThread::workerIsolate()
+{
+    if (!m_isolate) {
+        ASSERT(isCurrentThread());
+        m_isolate = CompositorWorkerManager::instance()->createIsolate();
+    }
+    return m_isolate;
 }
 
 } // namespace blink