Breakpoint source location matching with Chrome DevTools

[mjrgh]

The Chrome DevTools debugger seems to send set-breakpoint-by-URL requests with the file:/// prefix stripped out of the URL. This prevents breakpoints from ever getting set in the engine, because DebuggerBreakpoint::IsScriptMatch() matches on exact URL string. Matching "file:///X" to "X" and vice versa in that routine fixes it.