compositor-worker: Create a separate CompositorWorkerGlobalScope for compositor workers.

Source/core/workers/DedicatedWorkerThread.cpp

Index: Source/core/workers/DedicatedWorkerThread.cpp
diff --git a/Source/core/workers/DedicatedWorkerThread.cpp b/Source/core/workers/DedicatedWorkerThread.cpp
index 80f22868d63fb8f4f27f56f5fe3fa3babef97143..2b4c7fb907f42d98d42c7edd46b9103f7fa6952f 100644
--- a/Source/core/workers/DedicatedWorkerThread.cpp
+++ b/Source/core/workers/DedicatedWorkerThread.cpp
@@ -56,7 +56,7 @@ DedicatedWorkerThread::~DedicatedWorkerThread()
 
 PassRefPtrWillBeRawPtr<WorkerGlobalScope> DedicatedWorkerThread::createWorkerGlobalScope(PassOwnPtrWillBeRawPtr<WorkerThreadStartupData> startupData)
 {
-    return DedicatedWorkerGlobalScope::create(this, startupData, m_timeOrigin);
+    return DedicatedWorkerGlobalScope::create(this, startupData, timeOrigin());
 }
 
 void DedicatedWorkerThread::postInitialize()