Enable -Wall on Linux as well.

Source/config.gyp

 #
 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 71 matching lines @@
         ['gcc_version>=46', {
           # Disable warnings about c++0x compatibility, as some names (such as
           # nullptr) conflict with upcoming c++0x types.
           'cflags_cc': ['-Wno-c++0x-compat'],
         }],
         ['OS=="linux" and target_arch=="arm"', {
           # Due to a bug in gcc arm, we get warnings about uninitialized
           # timesNewRoman.unstatic.3258 and colorTransparent.unstatic.4879.
           'cflags': ['-Wno-uninitialized'],
         }],
-        ['OS=="mac"', {
+        ['OS=="mac" or OS=="linux"', {
           # TODO: Turn this on on all platforms, http://crbug.com/312287
           'variables': {
             'chromium_code': 1,
           },
         }],
         ['clang==1', {
           'cflags': ['-Wglobal-constructors'],
           'xcode_settings': {
             'WARNING_CFLAGS': ['-Wglobal-constructors'],
           },
@@ skipping 16 matching lines @@
     ],
     'direct_dependent_settings': {
       'cflags!': ['-Wglobal-constructors'],
       'xcode_settings': {
         'WARNING_CFLAGS!': ['-Wglobal-constructors'],
       },
     },
   }
   ],
 }