Disable garbage collection for gyp_chromium.

Disable garbage collection for gyp_chromium.

Python always does reference counting and that handles most of the
objects used by GYP. The GC is used to detect and drop circular
references. If GC is turned off then the heap scanning can be skipped
to save some CPU cycles, and the memory leaked due to circular
references isn't noticeable.

This saves about 1 second out of 16 on Linux in a Z620 workstation.

BUG=None

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=291287

[Joao da Silva, 2014-08-21 14:54:59]

Hey Brett, can you have a look?

Turns out that this idea gives a little win in total runtime. Do you think it's
worth merging this change?

I saw 1s to 1.5s improvements on a Z620 with Linux (16s -> 15s) and on a 2011
Mac Pro (30s -> 28.5s), after running ~5 times with and without the patch.

[brettw, 2014-08-21 19:46:37]

lgtm

[Joao da Silva, 2014-08-21 21:32:34]

The CQ bit was checked by joaodasilva@chromium.org

[commit-bot: I haz the power, 2014-08-21 21:36:40]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/joaodasilva@chromium.org/495993002/20001

[commit-bot: I haz the power, 2014-08-21 23:04:59]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_dbg_tests_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_dbg_tes...)

[commit-bot: I haz the power, 2014-08-22 01:07:08]

Committed patchset #2 (20001) as 291287