Bug 897089 - [Clock] Utility methods pollute global scope r=ianliu

Organizing utility methods under a single namespace increases code
readability and minimizes global namespace pollution.
Bug 897090 - [Clock] L10n mocking is fragmented across test files r=ianliu
Bug 897117 - [Clock] ClockView methods are not fully covered by unit tests r=ianliu

This commit also fixes a bug in the tested method's implementation,
where the minute boundary was being calculated incorrectly. This bug
would induce the method to asynchronously recurse during the second of
time before the minute rolled over.
Make ClockView unit tests time zone independent