IDL compiler: v8SetReturnValueForMainWorld

Used on attributes and methods with interface return types
and [PerWorldBindings] in Node interfaces.
(Added test cases.)

27 => 23

BUG=239771
R=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/133193005

git-svn-id: svn://svn.chromium.org/blink/trunk@166382 bbb929c8-8fbe-4397-9dbb-9b2b20218538