compositor-worker: Create a separate CompositorWorkerGlobalScope 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 5672a35a20f9296627eb2a87de116b5c0b088743..7456e684d4bc89a45a1ae45d625051d74a58fb60 100644
--- a/Source/modules/compositorworker/CompositorWorkerThread.cpp
+++ b/Source/modules/compositorworker/CompositorWorkerThread.cpp
@@ -8,6 +8,7 @@
 #include "bindings/core/v8/V8Initializer.h"
 #include "core/workers/WorkerObjectProxy.h"
 #include "core/workers/WorkerThreadStartupData.h"
+#include "modules/compositorworker/CompositorWorkerGlobalScope.h"
 #include "public/platform/Platform.h"
 
 namespace blink {
@@ -27,6 +28,11 @@ CompositorWorkerThread::~CompositorWorkerThread()
 {
 }
 
+PassRefPtrWillBeRawPtr<WorkerGlobalScope> CompositorWorkerThread::createWorkerGlobalScope(PassOwnPtrWillBeRawPtr<WorkerThreadStartupData> startupData)
+{
+    return CompositorWorkerGlobalScope::create(this, startupData, timeOrigin());
+}
+
 v8::Isolate* CompositorWorkerThread::initializeIsolate()
 {
     return WorkerThread::initializeIsolate();