resourceloader: Simplify and clean up RLQ wrap

resourceloader: Simplify and clean up RLQ wrap

startup.js:
* Don't assign to "window.RLQ" and read from "RLQ". Use the same
  identifier in both places instead of relying on global scope.
* Create the global window.RLQ only once. The temporary [] fallback
  doesn't need to be exposed globally, so use a local variable for
  the loop that processes the pre-existing queue built up while
  the startup module was loading.

OutputPage:
* Simplify the RLQ wrap to be more idiomatic and less repetitive.
  Matches the pattern used in Google and Facebook open-source projects.

Change-Id: I9176377bc05432e51add841696a356428feec8ce