Add an LRUBoundedCache class.

Add an LRUBoundedCache class.

This class is simpler to use than media/blink/lru.h for the purpose of bounding
the memory usage of a simple cache.

ios/chrome/browser/snapshots/lru_cache.h performs the same job as this class,
but is in Objective-C++ for iOS; in a future CL, this class could potentially
replace the Objective-C++ code.

BUG=598899

[palmer, 2016-04-09 00:25:11]

Description was changed from

==========
Add an LRUBoundedCache class.

This class is simpler to use than media/blink/lru.h for the purpose of bounding
the memory usage of a simple cache.

ios/chrome/browser/snapshots/lru_cache.h performs the same job as this class,
but is in Objective-C++ for iOS; in a future CL, this class could potentially
replace the Objective-C++ code.
==========

to

==========
Add an LRUBoundedCache class.

This class is simpler to use than media/blink/lru.h for the purpose of bounding
the memory usage of a simple cache.

ios/chrome/browser/snapshots/lru_cache.h performs the same job as this class,
but is in Objective-C++ for iOS; in a future CL, this class could potentially
replace the Objective-C++ code.

BUG=598899
==========

[palmer, 2016-04-09 00:27:50]

palmer@chromium.org changed reviewers:
+ mmenke@chromium.org

[palmer, 2016-04-09 00:27:51]

See if you think this makes any sense. Thanks!

[mmenke, 2016-04-11 16:12:25]

On 2016/04/09 00:27:51, palmer wrote:
> See if you think this makes any sense. Thanks!

Going to hold off on this review until we've decided if
base/containers/mru_cache.h will work for our use case.

[palmer, 2016-04-11 21:50:58]

> Going to hold off on this review until we've decided if
> base/containers/mru_cache.h will work for our use case.

Ahh, very good, I hadn't seen that. I think I need to add a Contains member
function, and for space-efficiency we might want to make a std::set variant.
I'll fire up a CL for that, and close this one. Thanks!