https://bugzilla.mozilla.org/show_bug.cgi?id=1342012
Support import from timeout handlers by associating the initiating script with the compiled JSScript.
Fix error message that covers all import() failures that don't throw a JS exception.
https://bugzilla.mozilla.org/show_bug.cgi?id=1331662
Partial - Replace nsJSUtils::EvaluateString calls by ExecutionContext scopes.
Left EvaluateString() in nsXBLProtoImplField.cpp until ExecutionContext errors can be fixed.
(cherry picked from commit 22fcfc77971a9bb204df664c474681f4dcf54211)