resourceloader: Remove redundant closure of some startup and base files
* errorLogger: Contains only top-level assignments and statements,
no scope needed. If it does need a scope at some point, then it
should be converted to packageFiles first so that the closure
still isn't needed (see T50886).
* requestIdleCallback: This file should do nothing in modern browsers,
except alias a native method, and expose the fallback for testing.
Remove the closure and with it the (usually) unused local var.
* mediawiki.js: Use the shorter Object.hasOwnProperty instead,
we already do this in several files. Both provide a quick reference
to the native method. Object.prototype.hasOwnProperty is more direct
visually, but also less direct at run-time (3 lookups instead of 2).
MW does not support environments that extend native classes such as
Object or their prototypes, so this makes no difference in that
regard and is already done in several core files. (More wide changes
to be done separately).
Change-Id: I98ed4da4807c54254669053cef47a3e67b4ad2cf