Enable /GL for all targets in Official (behind a flag)

third_party/mesa/BUILD.gn

Index: third_party/mesa/BUILD.gn
diff --git a/third_party/mesa/BUILD.gn b/third_party/mesa/BUILD.gn
index 01e4ad427236040984b150e870cab850d00fe462..0c90820315b343905849a6df0f9558d244764fc3 100644
--- a/third_party/mesa/BUILD.gn
+++ b/third_party/mesa/BUILD.gn
@@ -144,6 +144,11 @@ config("mesa_internal_warnings") {
       "/wd4345",  # POD-type default initializers.
       "/wd4311",  # Pointer truncation TODO(brucedawson): http://crbug.com/554200
     ]
+    if (is_official_build && full_wpo_on_official) {
+      # TODO(sebmarchand): http://crbug.com/604838 This should be removed if
+      # Mesa is ever rolled and the warnings is fixed.

[brucedawson, 2016/04/29 00:06:13]

nit: warnings -> warning (or is -> are)

[Sébastien Marchand, 2016/04/29 14:15:39]

Done.

+      cflags += [ "/wd4723" ]  # potential divide by 0.
+    }
   }
 }