Add a new gyp flag to enable resource whitelist generation.

BUG=338759
NOTRY=true

Review URL: https://codereview.chromium.org/184783005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255710 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255710