Add 'base::Time::Max()' to explicitly refer to the end of time.

Add 'base::Time::Max()' to explicitly refer to the end of time.

BrowingDataRemover (and, I imagine, other systems) recognized ranges bounded by null Time objects ('base::Time()') as referring to "everything". That introduces easily-forgotten complexity, which leads to avoidable mistakes in logic. This CL provides a mechanism for avoiding this sort of confusion in the future by adding the ability to explicitly refer to the end of time via 'base::Time::Max()'.

It simply returns a Time object whose internal counter is set to the maximum int64, which means that simple comparisons like 'time <= end' will do The Right Thing™.

BUG=144972
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=153514

[Mike West, 2012-08-27 14:48:51]

Hi Mark! I picked a name more or less at random from the base/OWNERS file, so I
do hope you have a few moments to take a look at this CL.

TL;DR: This CL adds a `Max()` method to `base::Time` in the hopes of making
ranges that intentionally include the entire future explicit.

I hope the CL description describes the goal in enough detail for you to
evaluate the desirability of the addition. If not, I'm happy to provide whatever
detail you'd like.

Thanks!

-mike

[Mark Mentovai, 2012-08-27 15:38:08]

LGTM

[commit-bot: I haz the power, 2012-08-27 16:23:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mkwst@chromium.org/10883061/1

[commit-bot: I haz the power, 2012-08-27 18:44:05]

Change committed as 153514