GN args threading and error enhancements.
The locking in the args object was not very consistent which is a likely cause of flakyness. This patch makes it clear what should be locked and what shouldn't be.
It also enhances the error reporting to list all possible args on error to help me debug an issue on a bot.
TBR=scottmg
Review URL: https://codereview.chromium.org/132703004
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249300 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed
