Worker: Clarify a target context of postTask in WorkerEventQueue

third_party/WebKit/Source/core/workers/WorkerGlobalScope.h

Index: third_party/WebKit/Source/core/workers/WorkerGlobalScope.h
diff --git a/third_party/WebKit/Source/core/workers/WorkerGlobalScope.h b/third_party/WebKit/Source/core/workers/WorkerGlobalScope.h
index a582d4489cbeebea5007b8040f55c7845b55d993..9059e9bd032285bc9e4d350c771092773c66de23 100644
--- a/third_party/WebKit/Source/core/workers/WorkerGlobalScope.h
+++ b/third_party/WebKit/Source/core/workers/WorkerGlobalScope.h
@@ -124,10 +124,14 @@ class CORE_EXPORT WorkerGlobalScope : public EventTargetWithInlineData,
   bool isContextThread() const final;
   void disableEval(const String& errorMessage) final;
   String userAgent() const final { return m_userAgent; }
+
+  // This is necessary to make parent's postTask visible.
+  using ExecutionContext::postTask;
   void postTask(TaskType,
                 const WebTraceLocation&,
                 std::unique_ptr<ExecutionContextTask>,
                 const String& taskNameForInstrumentation) final;
+
   DOMTimerCoordinator* timers() final { return &m_timers; }
   SecurityContext& securityContext() final { return *this; }
   void addConsoleMessage(ConsoleMessage*) final;