Support multiple voices for all available modules (text-to-speech engines) on Linux.

build/linux/system.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': {
     'conditions': [
       ['sysroot!=""', {
         'pkg-config': './pkg-config-wrapper "<(sysroot)" "<(target_arch)"',
       }, {
@@ skipping 502 matching lines @@
                      '--bundled-header',
                      '"third_party/speech-dispatcher/libspeechd.h"',
                      '--link-directly=<(linux_link_libspeechd)',
                      'spd_open',
                      'spd_say',
                      'spd_stop',
                      'spd_close',
                      'spd_set_notification_on',
                      'spd_set_voice_rate',
                      'spd_set_voice_pitch',
+                     'spd_list_synthesis_voices',
+                     'spd_set_synthesis_voice',
+                     'spd_list_modules',
+                     'spd_set_output_module',
           ],
           'message': 'Generating libspeechd library loader.',
           'process_outputs_as_sources': 1,
         },
       ],
     },
     {
       'target_name': 'x11',
       'type': 'none',
       'toolsets': ['host', 'target'],
@@ skipping 288 matching lines @@
             ],
             'libraries': [
               '<!@(<(pkg-config) --libs-only-l libudev)',
             ],
           },
         }],
       ],
     },
   ],
 }