Enable --nacl-gdb flag on Linux.

chrome/chrome_tests.gypi

 # 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' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
       'common/pref_names.cc',
@@ skipping 3019 matching lines @@
         ['disable_nacl==0', {
           'sources':[
             'browser/extensions/extension_nacl_browsertest.cc',
           ],
           'conditions': [
             ['disable_nacl_untrusted==0', {
               'dependencies': [
               '../ppapi/ppapi_untrusted.gyp:ppapi_nacl_tests',
               ],
             }],
-            # TODO(halyavin): Implement this test for linux.
-            ['OS=="win"', {
+            ['OS=="win" or OS=="linux"', {
               'sources': [
                 'browser/nacl_host/test/nacl_gdb_browsertest.cc',
               ],
               'dependencies': [
                 'browser/nacl_host/test/mock_nacl_gdb.gyp:mock_nacl_gdb',
               ],
             }],
           ],
         }],
         ['chromeos==0', {
@@ skipping 1612 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],  # 'coverage!=0'
   ],  # 'conditions'
 }