IDL compiler: [Reflect] for getters

A pretty complicated one, with *lots* of special cases,
but managed to make it pretty simple.
(There's some additional special handling for SVG that
we're skipping for now.)

Doc:
https://sites.google.com/a/chromium.org/dev/blink/webidl/blink-idl-extended-attributes#TOC-Reflect-a-

BUG=239771
NOTRY=true
R=haraken@chromium.org

Review URL: https://codereview.chromium.org/27003002

git-svn-id: svn://svn.chromium.org/blink/trunk@159738 bbb929c8-8fbe-4397-9dbb-9b2b20218538