GN: toolchain threading cleanup

GN: toolchain threading cleanup

Remove the thread-unsafe toolchain pointer on the otherwise-threadsafe Settings object. I replaced it with the toolchain label, and moved the is_default flag from the toolchain to the Settings object.

This required that I pass the toolchain around in a few more places, but also simplifies some other cases.

I removed the toolchain prefix from Ninja rules for the default toolchain since that's not necessary any more for GYP compat.

This fixes an annoying double-free in the toolchain manager. I think my current refactor will clean this up in a later phase.

R=scottmg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=232657

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=232755

[scottmg, 2013-10-31 20:38:46]

lgtm

[commit-bot: I haz the power, 2013-11-02 20:57:30]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/brettw@chromium.org/51693002/40001

[commit-bot: I haz the power, 2013-11-02 21:15:37]

Retried try job too often on chromium_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=chromium_p...

[brettw, 2013-11-03 04:35:56]

Committed patchset #2 manually as r232657 (presubmit successful).

[brettw, 2013-11-04 19:20:35]

Committed patchset #2 manually as r232755 (presubmit successful).