linux: turn on -Wextra

build/common.gypi

 # Copyright (c) 2010 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   'variables': {
     # .gyp files or targets should set chromium_code to 1 if they build
@@ skipping 686 matching lines @@
           'conditions': [['OS=="linux"', {'werror%': '-Werror',}],
                          ['OS=="freebsd"', {'werror%': '',}],
                          ['OS=="openbsd"', {'werror%': '',}],
           ],
         },
         'cflags': [
           '<(werror)',  # See note above about the werror variable.
           '-pthread',
           '-fno-exceptions',
           '-Wall',
-          # TODO(evan): turn this back on once the v8 change lands.
-          #'-Wextra',
+          '-Wextra',
           # Don't warn about unused function params.  We use those everywhere.
           '-Wno-unused-parameter',
           # Don't warn about the "struct foo f = {0};" initialization pattern.
           '-Wno-missing-field-initializers',
           '-D_FILE_OFFSET_BITS=64',
           # Don't export any symbols (for example, to plugins we dlopen()).
           # Note: this is *required* to make some plugins work.
           '-fvisibility=hidden',
         ],
         'cflags_cc': [
@@ skipping 514 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
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