IDL compiler: [PerWorldBindings] getters

Relatively complicated one, due to:
* generating additional functions (hence changes overall attributes loop)
* interaction with [ActivityLogging]

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

Review URL: https://codereview.chromium.org/26805005

git-svn-id: svn://svn.chromium.org/blink/trunk@159809 bbb929c8-8fbe-4397-9dbb-9b2b20218538