WebCore class renames

• Frame → BrowsingContext
• FrameView → BrowsingContextView
• Page → View | Tab | MainBrowsingContextHolder

• RenderView → RenderRoot (also needs some functionality split out for SVG foreign object support)

• ScriptController→ DOMWindowProxy
• JSDOMWindowShell → JSDOMWindowProxy

• DatasetDOMStringMap → DOMStringMap

• FrameLoader → ?
• SubframeLoader → ?
• DocumentLoader → ?
• ThreadableLoader → ?
• DocumentThreadableLoader → ?
• WorkerThreadableLoader → ?