Basic experimental suborigin CSP directive and SecurityOrigin mods

Source/core/workers/WorkerGlobalScope.h

Index: Source/core/workers/WorkerGlobalScope.h
diff --git a/Source/core/workers/WorkerGlobalScope.h b/Source/core/workers/WorkerGlobalScope.h
index 69b4cff7a8f426a64c0f2a71da7ec27f46d23f73..e3fd51aa339fd9e2531c37e46455ff47576fa81c 100644
--- a/Source/core/workers/WorkerGlobalScope.h
+++ b/Source/core/workers/WorkerGlobalScope.h
@@ -111,7 +111,7 @@ public:
 
     // ExecutionContextClient
     WorkerEventQueue* eventQueue() const override final;
-    const SecurityContext& securityContext() const override final { return *this; }
+    SecurityContext& securityContext() override final { return *this; }
 
     bool isContextThread() const override final;
     bool isJSExecutionForbidden() const override final;