Long press menu (shift+f6) to toggle spoken feedback.

ash/ash.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': {
     'chromium_code': 1,
     'grit_out_dir': '<(SHARED_INTERMEDIATE_DIR)/chrome',
   },
   'includes': [
@@ skipping 46 matching lines @@
         'accelerators/accelerator_dispatcher.cc',
         'accelerators/accelerator_dispatcher.h',
         'accelerators/accelerator_filter.cc',
         'accelerators/accelerator_filter.h',
         'accelerators/accelerator_table.cc',
         'accelerators/accelerator_table.h',
         'accelerators/debug_commands.cc',
         'accelerators/debug_commands.h',
         'accelerators/exit_warning_handler.cc',
         'accelerators/exit_warning_handler.h',
+        'accelerators/key_hold_detector.cc',
+        'accelerators/key_hold_detector.h',
         'accelerators/focus_manager_factory.cc',
         'accelerators/focus_manager_factory.h',
         'accelerators/nested_dispatcher_controller.cc',
         'accelerators/nested_dispatcher_controller.h',
+        'accelerators/spoken_feedback_toggler.cc',
+        'accelerators/spoken_feedback_toggler.h',
         'accessibility_delegate.h',
         'audio/sounds.cc',
         'audio/sounds.h',
         'autoclick/autoclick_controller.cc',
         'autoclick/autoclick_controller.h',
         'ash_constants.cc',
         'ash_constants.h',
         'ash_switches.cc',
         'ash_switches.h',
         'cancel_mode.cc',
@@ skipping 552 matching lines @@
           'msvs_disabled_warnings': [ 4267, ],
         }],
         ['OS!="linux"', {
           'sources/': [
             ['exclude', 'system/monitor/tray_monitor.cc'],
             ['exclude', 'system/monitor/tray_monitor.h'],
           ],
         }],
         ['use_x11!=1', {
           'sources/': [
+            ['exclude', 'accelerators/spoken_feedback_toggler.cc'],
+            ['exclude', 'accelerators/spoken_feedback_toggler.h'],
             ['exclude', 'display/display_change_observer_chromeos.cc'],
             ['exclude', 'display/display_change_observer_chromeos.h'],
             ['exclude', 'display/display_error_observer_chromeos.cc'],
             ['exclude', 'display/display_error_observer_chromeos.h'],
             ['exclude', 'magnifier/magnifier_key_scroller.cc'],
             ['exclude', 'magnifier/magnifier_key_scroller.h'],
           ],
         }],
         ['chromeos==1', {
           'dependencies': [
@@ skipping 168 matching lines @@
         'ash_resources',
         'ash_test_support',
         'ash_with_content',
       ],
       'sources': [
         'accelerators/accelerator_commands_unittest.cc',
         'accelerators/accelerator_controller_unittest.cc',
         'accelerators/accelerator_filter_unittest.cc',
         'accelerators/accelerator_table_unittest.cc',
         'accelerators/nested_dispatcher_controller_unittest.cc',
+        'accelerators/spoken_feedback_toggler_unittest.cc',
         'autoclick/autoclick_unittest.cc',
         'desktop_background/desktop_background_controller_unittest.cc',
         'desktop_background/wallpaper_resizer_unittest.cc',
         'dip_unittest.cc',
         'display/display_change_observer_chromeos_unittest.cc',
         'display/display_controller_unittest.cc',
         'display/display_error_observer_chromeos_unittest.cc',
         'display/display_info_unittest.cc',
         'display/display_manager_unittest.cc',
         'display/mirror_window_controller_unittest.cc',
@@ skipping 133 matching lines @@
           # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
           'msvs_disabled_warnings': [ 4267, ],
         }],
         ['OS=="win" and win_use_allocator_shim==1', {
           'dependencies': [
             '../base/allocator/allocator.gyp:allocator',
           ],
         }],
         ['use_x11!=1', {
           'sources/': [
+            ['exclude', 'accelerators/spoken_feedback_toggler_unittest.cc'],
             ['exclude', 'display/display_change_observer_chromeos_unittest.cc'],
             ['exclude', 'display/display_error_observer_chromeos_unittest.cc'],
             ['exclude', 'magnifier/magnifier_key_scroller_unittest.cc'],
           ],
         }],
         ['chromeos==1', {
           'dependencies': [
             '../chromeos/chromeos.gyp:power_manager_proto',
           ],
           'sources': [
@@ skipping 91 matching lines @@
             },
           },
           'dependencies': [
             '../sandbox/sandbox.gyp:sandbox',
           ],
         }],
       ],
     },
   ],
 }