Extract a DOMWindow interface from LocalDOMWindow and use it in the idl.

Source/core/frame/LocalFrame.cpp

Index: Source/core/frame/LocalFrame.cpp
diff --git a/Source/core/frame/LocalFrame.cpp b/Source/core/frame/LocalFrame.cpp
index 9b5c504e0f6067fc848f2cc4baf8190d42305db8..12bb49b85fc5f79348562943e4c7cc491071d970 100644
--- a/Source/core/frame/LocalFrame.cpp
+++ b/Source/core/frame/LocalFrame.cpp
@@ -241,7 +241,7 @@ void LocalFrame::trace(Visitor* visitor)
     Frame::trace(visitor);
 }
 
-LocalDOMWindow* LocalFrame::domWindow() const
+DOMWindow* LocalFrame::domWindow() const

[haraken, 2014/11/08 09:17:25]

Can we remove this method?

DOMWindow* window = localFrame()->localDOMWindow();

will just work. It looks confusing to have both domWindow() and
localDOMWindow().

[dcheng, 2014/11/08 23:59:56]

The main reason we have localDOMWindow() is because I can't use covariant
returns for both LocalFrame::domWindow() and LocalDOMWindow::frame(), since this
would be a circular dependency. So instead, we expose the local version through
a non-virtual getter.

Unfortunately, removing either leads to uglier code elsewhere:
1. The reason we have this exposed as an overridable method on Frame is to
simplify code like DOMWindow::top(). Without this virtual, DOMWindow::top()
would have to look like:
    Frame* f = frame()->tree()->top();
    return f->isLocalFrame() ?
static_cast<DOMWindow*>(toLocalFrame(f)->localDOMWindow())
        : toRemoteFrame(f)->remoteDOMWindow();

2. The reason we have LocalFrame::localDOMWindow() is to prevent useless casts.
For example, DOMWindowProperty is always associated with a LocalFrame atm.
Without localDOMWindow(), the code would change from:
#if ENABLE(OILPAN)
        m_frame->localDOMWindow()->registerProperty(this);
#else
        m_associatedDOMWindow = m_frame->localDOMWindow();
        m_associatedDOMWindow->registerProperty(this);
#endif

to:
#if ENABLE(OILPAN)
        toLocalDOMWindow(m_frame->DOMWindow())->registerProperty(this);
#else
        m_associatedDOMWindow = toLocalDOMWindow(m_frame->localDOMWindow());
        m_associatedDOMWindow->registerProperty(this);
#endif

This cast is pointless, because we always have LocalFrames here, and LocalFrames
must have LocalDOMWindows.

[haraken, 2014/11/10 08:58:20]

Makes sense.

 {
     return m_domWindow.get();
 }