Add a basic DOMWindow base class and use it in WindowProxy.

Source/core/frame/Frame.cpp

Index: Source/core/frame/Frame.cpp
diff --git a/Source/core/frame/Frame.cpp b/Source/core/frame/Frame.cpp
index 7c67e4c098a62252b04a640f1bac78b6847e65b6..cc04f692752cab7a1c1c01af6fb82ed9b16099d9 100644
--- a/Source/core/frame/Frame.cpp
+++ b/Source/core/frame/Frame.cpp
@@ -60,11 +60,6 @@ DEFINE_DEBUG_ONLY_GLOBAL(WTF::RefCountedLeakCounter, frameCounter, ("Frame"));
 Frame::~Frame()
 {
     ASSERT(!m_owner);
-#if !ENABLE(OILPAN)
-    // FIXME: We should not be doing all this work inside the destructor
-    setDOMWindow(nullptr);
-#endif
-
 #ifndef NDEBUG
     frameCounter.decrement();
 #endif
@@ -75,7 +70,6 @@ void Frame::trace(Visitor* visitor)
     visitor->trace(m_treeNode);
     visitor->trace(m_host);
     visitor->trace(m_owner);
-    visitor->trace(m_domWindow);
 }
 
 void Frame::detach()
@@ -143,14 +137,6 @@ HTMLFrameOwnerElement* Frame::deprecatedLocalOwner() const
     return m_owner && m_owner->isLocal() ? toHTMLFrameOwnerElement(m_owner) : 0;
 }
 
-void Frame::setDOMWindow(PassRefPtrWillBeRawPtr<LocalDOMWindow> domWindow)
-{
-    if (m_domWindow)
-        m_domWindow->reset();
-
-    m_domWindow = domWindow;
-}
-
 static ChromeClient& emptyChromeClient()
 {
     DEFINE_STATIC_LOCAL(EmptyChromeClient, client, ());