Making V8PerIsolateData::hasInstance do the check according to the passed world type uncovers problems:
- v8::Handle<v8::Value> V8Document::evaluateMethodCustom(const v8::Arguments& args) seems to have the wrong node (main world instead of isolated world) in args, and HasInstance fails there. -> ExecuteScriptApiTest.ExecuteScriptFrameAfterLoad (chromium browser_tests) fails
- crash in contextHasCorrectPrototype -> ExecuteScriptApiTest.ExecuteScriptCallback (chromium browser_tests) fails.
This got done as a side effect of some other patch. We need to check multiple worlds in some cases though (if we're going through NPAPI, we don't have a context and can't get the world from there).