base: Add uncached malloc based discardable memory type.

base: Add uncached malloc based discardable memory type.

Each DiscardableMemoryMalloc instance uses a separate malloc() allocated block
of memory. It's allocated on Lock() and freed on Unlock().

This is useful to test how discardable memory clients perform in situations
when the memory pressure is high. The base class will also be used by other
discardable memory implementations as a fall-back when failing to
allocate/lock native discardable memory.

BUG=334996
TEST=base_unittests --gtest_filter=DiscardableMemoryTests*

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=250167

[Philippe, 2014-02-06 11:47:23]

lgtm, thanks!

[reveman, 2014-02-10 05:32:21]

Ok, let's land this so we can use it both for testing and as a fallback.
willchan@, please take a look.

[willchan no longer on Chromium, 2014-02-10 06:44:22]

LGTM

I updated your changelist description to include more implementations details,
obviously feel free to correct it and add more if that makes sense. It'd also be
great to explain how you plan to use it. And if you have a BUG for this, it'd be
great to link that.

[reveman, 2014-02-10 17:07:04]

On 2014/02/10 06:44:22, willchan wrote:
> LGTM
> 
> I updated your changelist description to include more implementations details,
> obviously feel free to correct it and add more if that makes sense. It'd also
be
> great to explain how you plan to use it. And if you have a BUG for this, it'd
be
> great to link that.

Thanks. I added BUG+TEST and explained how this will be used.

[reveman, 2014-02-10 17:07:14]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-02-10 17:07:55]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/reveman@chromium.org/145643008/1

[commit-bot: I haz the power, 2014-02-10 19:19:32]

Change committed as 250167