Add unit tests for base::GetSystemMemoryInfo

Add unit tests for base::GetSystemMemoryInfo

BUG=176044
TEST=base_unittests ProcessUtilTest

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=182540

[James Cook, 2013-02-13 19:18:33]

davemoore, PTAL

This also leaves a place to add tests for gem_objects when that starts working
again.

[DaveMoore, 2013-02-13 19:24:26]

lgtm

[James Cook, 2013-02-13 19:26:04]

will, can I get OWNERS approval for this test?

[willchan no longer on Chromium, 2013-02-13 19:33:15]

I almost thought I could do this review, but I'm too sick to consider any
flakiness consequences. I'm going to have to punt. I recommend jar@ for this
memory stuff.

The main thing that made my head hurt was looking at the test to make sure the
values you're comparing against aren't racy due to memory allocations that may
happen in other threads (some base unittests start up threads and don't join
them by the end of their test).

[James Cook, 2013-02-13 19:52:07]

jar, can I get OWNERS approval for this test?

will, thanks for the comments. I backed out the testing for anonymous memory
usage going up after an allocation - if other threads are releasing memory I
can't make system-wide assertions about the state of things.

Also, I just found out that base_unittests aren't actually running on Chrome OS
hardware right now, so I backed out the check for IsRunningOnChromeOS().  :-( 
Shmem should be OK on our try bots.

[jar (doing other things), 2013-02-14 02:26:11]

LGTM with nit

https://codereview.chromium.org/12257013/diff/8001/base/process_util_unittest.cc
File base/process_util_unittest.cc (right):

https://codereview.chromium.org/12257013/diff/8001/base/process_util_unittest...
base/process_util_unittest.cc:385: base::SystemMemoryInfoKB info1;
nit: how about using the name |info|.

I assume you used to have others.