gpu/gles2_conform_support: On Chrome OS, don't use system.gyp to pull in GTK+

Normally, gles2_conform_support uses system.gyp:gtk to pull in a system copy
of GTK+; however, Chrome OS already installs GTK+, and system.gyp
intentionally does not provide a gtk target on Chrome OS.  Make the
dependencies on system.gyp:gtk conditional on 'chromeos==0'.

BUG=chromium:388784
TEST=Manually build gles2_conform_test on Chrome OS
[email protected], [email protected]

Review URL: https://codereview.chromium.org/355453003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@280227 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/AUTHORS b/AUTHORS
index 80baa98..4f22c65f 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -189,6 +189,7 @@
 Joone Hur <[email protected]>
 Jorge Villatoro <[email protected]>
 Joseph Gentle <[email protected]>
+Josh Triplett <[email protected]>
 Josh Triplett <[email protected]>
 Joshua Lock <[email protected]>
 Joshua Roesslein <[email protected]>