Switch custom XMLHttpRequest bindings over to new-style ExceptionState.

Configure incoming ExceptionState with the calling context instead of
detailing at the point where the exception is raised.

To support throwing context-sensitive TypeErrors, extend
ExceptionState::throwTypeError() to also embellish its incoming
messages.

R=mkwst
BUG=270033

Review URL: https://codereview.chromium.org/96793002

git-svn-id: svn://svn.chromium.org/blink/trunk@162909 bbb929c8-8fbe-4397-9dbb-9b2b20218538