Revert of https://codereview.chromium.org/83773002/
Reason for revert: Speculatively reverting to fix the cros breakage: http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%282%29/builds/10024

TBR=acleung@chromium.org,guohui@chromium.org,atwilson@chromium.org,rogerta@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=320351

Review URL: https://codereview.chromium.org/120653002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242355 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242355
Add GN conversions for flags

Adds a remapping from important GYP flags used on the main waterfall for GN. For the other ones, I added a list of used flags and filed bugs for them.

R=scottmg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/119803002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242356 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242356