Enable -Wself-assign-memvar for Mesa, merge upstream fix for the one violation

third_party/mesa/mesa.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
   },
   'target_defaults': {
     'conditions': [
       ['OS!="win"', {
@@ skipping 508 matching lines @@
       ],
       'conditions': [
         ['clang == 1', {
           'xcode_settings': {
             'WARNING_CFLAGS': [
               # Several functions ignore the result of talloc_steal().
               '-Wno-unused-value',
               # texenvprogram.c converts '~0' to a bitfield, which causes clang
               # to warn that -1 is implicitly converted to 255.
               '-Wno-constant-conversion',
-              # https://bugs.freedesktop.org/show_bug.cgi?id=51574
-              '-Wno-self-assign-memvar',
             ],
           },
           'cflags': [
             '-Wno-unused-value',
             '-Wno-constant-conversion',
-            '-Wno-self-assign-memvar',
           ],
         }],
       ],
     },
     # Building this target will hide the native OpenGL shared library and
     # replace it with a slow software renderer.
     {
       'target_name': 'osmesa',
       'type': 'loadable_module',
       'mac_bundle': 0,
@@ skipping 18 matching lines @@
         'MesaLib/src/mesa/drivers/common/driverfuncs.c',
         'MesaLib/src/mesa/drivers/common/driverfuncs.h',
         'MesaLib/src/mesa/drivers/common/meta.c',
         'MesaLib/src/mesa/drivers/common/meta.h',
         'MesaLib/src/mesa/drivers/osmesa/osmesa.c',
         'MesaLib/src/mesa/drivers/osmesa/osmesa.def',
       ],
     },
   ],
 }