Make SecurityContext available in RemoteFrames.

Source/web/WebLocalFrameImpl.h

Index: Source/web/WebLocalFrameImpl.h
diff --git a/Source/web/WebLocalFrameImpl.h b/Source/web/WebLocalFrameImpl.h
index 068c4d518865f5bfb77192e32a32e3c0f2df514e..d5b00ac4846d8370d94bd0a9f3a1e397f24f813c 100644
--- a/Source/web/WebLocalFrameImpl.h
+++ b/Source/web/WebLocalFrameImpl.h
@@ -82,6 +82,7 @@ public:
     virtual void setRemoteWebLayer(WebLayer*) override;
     virtual void setPermissionClient(WebPermissionClient*) override;
     virtual void setSharedWorkerRepositoryClient(WebSharedWorkerRepositoryClient*) override;
+    virtual WebSecurityOrigin securityOrigin() const override;

[dcheng, 2014/11/19 00:53:55]

Just curious: what are your thoughts on implementing this directly in
WebFrame.cpp? We have two different ways of doing it right now--add a virtual
method and an implementation for Local/Remote like this patch does, or use the
toCoreFrame() helper in WebFrame.cpp like WebFrame::detach() does.

[alexmos, 2014/11/19 18:19:19]

That would work too.  In that case, WebFrame::securityOrigin would just be
"return
WebSecurityOrigin(toCoreFrame(frame)->securityContext()->securityOrigin())".  I
actually like this more - makes the patch smaller and doesn't duplicate the
LocalFrame's redirect-to-document behavior at the Web layer.  Any other reasons
why one would prefer one approach over the other?

[dcheng, 2014/11/19 18:28:38]

toCoreFrame:
Advantages: less code duplication, smaller WebFrame vtable.
Disadvantages: we pay for two virtual dispatches, unless the compiler is really
clever with toCoreFrame inlining.

WebFrame virtual:
Advantages: only pay for one virtual dispatch (theoretically; we forgot to make
LocalFrame/RemoteFrame final, but if they were...)
Disadvantages: code duplication, bigger WebFrame vtable.

I don't see an overwhelming advantage for one over the other. I personally lean
towards toCoreFrame() because of less code duplication, but more important is
consistently picking one way or another.

     virtual WebSize scrollOffset() const override;
     virtual void setScrollOffset(const WebSize&) override;
     virtual WebSize minimumScrollOffset() const override;