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

third_party/mesa/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
+import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 config("mesa_headers_config") {
   include_dirs = [ "src/include" ]
   if (!use_x11) {
     defines = [ "MESA_EGL_NO_X11_HEADERS" ]
   }
 }
 
 # This directory contains checked-in files generated from the Mesa build.
@@ skipping 121 matching lines @@
       "/wd4065",  # Switch statement contains 'default' but no 'case' labels.
       "/wd4090",  # 'Operation' : different 'modifier' qualifiers
       "/wd4099",  # Type name struct-vs-class doesn't match.
       "/wd4273",  # Inconsistent DLL linkage.
       "/wd4291",  # No matching operator delete found for placement new.
       "/wd4305",  # Truncation from int to float.
       "/wd4334",  # Result of 32-bit shift implicitly converted to 64 bits.
       "/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 warning is fixed.
+      cflags += [ "/wd4723" ]  # potential divide by 0.
+    }
   }
 }
 
 config("mesa_libglslcommon_warnings") {
   if (is_clang) {
     cflags = [
       # https://bugs.freedesktop.org/show_bug.cgi?id=91645:
       "-Wno-overloaded-virtual",
     ]
   }
@@ skipping 616 matching lines @@
     deps = [
       "//third_party/wayland:wayland_util",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
 
     public_configs = [ ":wayland_drm_protocol_config" ]
   }
 }