Basic experimental suborigin CSP directive and SecurityOrigin mods

Source/core/testing/NullExecutionContext.h

Index: Source/core/testing/NullExecutionContext.h
diff --git a/Source/core/testing/NullExecutionContext.h b/Source/core/testing/NullExecutionContext.h
index f31a1d5694098b2b3d59350646c4e519e4679b78..6ade2c19631ea64eb434b134e06640dbc23d085e 100644
--- a/Source/core/testing/NullExecutionContext.h
+++ b/Source/core/testing/NullExecutionContext.h
@@ -34,7 +34,7 @@ public:
 
     virtual void reportBlockedScriptExecutionToInspector(const String& directiveText) override { }
     virtual void didUpdateSecurityOrigin() override { }
-    virtual const SecurityContext& securityContext() const override { return *this; }
+    virtual SecurityContext& securityContext() override { return *this; }
     virtual DOMTimerCoordinator* timers() override { return nullptr; }
 
     double timerAlignmentInterval() const;