I believe that these are the currently-repeatable accelerators in ash:

BRIGHTNESS_DOWN
BRIGHTNESS_UP
DEBUG_ADD_REMOVE_DISPLAY
DEBUG_PRINT_LAYER_HIERARCHY
DEBUG_PRINT_VIEW_HIERARCHY
DEBUG_PRINT_WINDOW_HIERARCHY
DEBUG_SHOW_TOAST
DEBUG_TOGGLE_DESKTOP_BACKGROUND_MODE
DEBUG_TOGGLE_DEVICE_SCALE_FACTOR
DEBUG_TOGGLE_ROOT_WINDOW_FULL_SCREEN
DEBUG_TOGGLE_SHOW_DEBUG_BORDERS
DEBUG_TOGGLE_SHOW_FPS_COUNTER
DEBUG_TOGGLE_SHOW_PAINT_RECTS
DEBUG_TOGGLE_TOUCH_VIEW
DEBUG_TOGGLE_UNIFIED_DESKTOP
DISABLE_CAPS_LOCK
DISABLE_GPU_WATCHDOG
FOCUS_NEXT_PANE
FOCUS_PREVIOUS_PANE
FOCUS_SHELF
KEYBOARD_BRIGHTNESS_DOWN
KEYBOARD_BRIGHTNESS_UP
LAUNCH_APP_0
LAUNCH_APP_1
LAUNCH_APP_2
LAUNCH_APP_3
LAUNCH_APP_4
LAUNCH_APP_5
LAUNCH_APP_6
LAUNCH_APP_7
LAUNCH_LAST_APP
LOCK_PRESSED
LOCK_RELEASED
MAGNIFY_SCREEN_ZOOM_IN
MAGNIFY_SCREEN_ZOOM_OUT
MEDIA_NEXT_TRACK
MEDIA_PLAY_PAUSE
MEDIA_PREV_TRACK
NEW_INCOGNITO_WINDOW
NEW_TAB
NEW_WINDOW
OPEN_CROSH
OPEN_FILE_MANAGER
OPEN_GET_HELP
POWER_PRESSED
POWER_RELEASED
RESTORE_TAB
SHOW_KEYBOARD_OVERLAY
SHOW_MESSAGE_CENTER_BUBBLE
SHOW_SYSTEM_TRAY_BUBBLE
SHOW_TASK_MANAGER
SWAP_PRIMARY_DISPLAY
SWITCH_IME
SWITCH_TO_NEXT_USER
SWITCH_TO_PREVIOUS_USER
TOGGLE_APP_LIST
TOGGLE_CAPS_LOCK
TOGGLE_MIRROR_MODE
TOGGLE_SPOKEN_FEEDBACK
TOGGLE_WIFI
TOUCH_HUD_CLEAR
TOUCH_HUD_MODE_CHANGE
TOUCH_HUD_PROJECTION_TOGGLE
UNPIN
VOLUME_DOWN
VOLUME_MUTE
VOLUME_UP
WINDOW_CYCLE_SNAP_DOCK_LEFT
WINDOW_CYCLE_SNAP_DOCK_RIGHT
WINDOW_POSITION_CENTER

Of those, I think that the list of ones that we actually want to repeat is much shorter; probably something like this:

BRIGHTNESS_DOWN
BRIGHTNESS_UP
FOCUS_NEXT_PANE
FOCUS_PREVIOUS_PANE
KEYBOARD_BRIGHTNESS_DOWN
KEYBOARD_BRIGHTNESS_UP
MAGNIFY_SCREEN_ZOOM_IN
MAGNIFY_SCREEN_ZOOM_OUT
MEDIA_NEXT_TRACK
MEDIA_PREV_TRACK
RESTORE_TAB
VOLUME_DOWN
VOLUME_UP

I could be convinced otherwise about some of those, though:

- SCALE_UI_DOWN and SCALE_UI_UP are currently nonrepeatable. Should MAGNIFY_SCREEN_ZOOM_IN and MAGNIFY_SCREEN_ZOOM_OUT also be nonrepeatable?
- What about FOCUS_NEXT_PANE and FOCUS_PREVIOUS_PANE?
- What about RESTORE_TAB?

I only find RESTORE_TAB's current repeatability to be useful since Ctrl-W (handled by Chrome rather than ash) is repeatable and I sometimes trigger it accidentally. :-/

Your short list sounds good to me. I don't have an opinion about SCALE_UI, MAGNIFY_SCREEN, and FOCUS_*_PANE and would just leave them as they are.

RESTORE_TAB being repeatable is fine with me.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c061dd11ada8a97335b2ef9b13757cdb780f84e8

commit c061dd11ada8a97335b2ef9b13757cdb780f84e8
Author: derat <derat@chromium.org>
Date: Thu Jul 07 16:35:52 2016

ash: Explicitly enumerate repeatable accelerators.

Instead of designating specific accelerators as
non-repeatable (which is prone to getting outdated), keep
track of the few accelerators that should be repeatable.

Also make many probably-inadvertently-repeatable
accelerators instead be non-repeatable.

BUG= 626014 
TEST=manual

Review-Url: https://codereview.chromium.org/2130603002
Cr-Commit-Position: refs/heads/master@{#404161}

[modify] https://crrev.com/c061dd11ada8a97335b2ef9b13757cdb780f84e8/ash/accelerators/accelerator_controller.cc
[modify] https://crrev.com/c061dd11ada8a97335b2ef9b13757cdb780f84e8/ash/accelerators/accelerator_controller.h
[modify] https://crrev.com/c061dd11ada8a97335b2ef9b13757cdb780f84e8/ash/accelerators/accelerator_table.cc
[modify] https://crrev.com/c061dd11ada8a97335b2ef9b13757cdb780f84e8/ash/accelerators/accelerator_table.h
[modify] https://crrev.com/c061dd11ada8a97335b2ef9b13757cdb780f84e8/ash/accelerators/accelerator_table_unittest.cc
[modify] https://crrev.com/c061dd11ada8a97335b2ef9b13757cdb780f84e8/ash/accelerators/exit_warning_handler.h

Closing bug as per comment #3 and #4