The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/566a5a2b7579c276d818914b2f30688960c3aa98

commit 566a5a2b7579c276d818914b2f30688960c3aa98
Author: dtseng <dtseng@chromium.org>
Date: Mon Apr 17 19:41:08 2017

Support braille dot or chorded typing conversions to standard keyboard keys

This cl enables flexible keyboard commands from a braille display perkins keyboard.

Incrmental modifier typing:
A user can press the following keys to build a shortcut
- space+dots 2-5: control
space+dots 3-6: alt
space+dots 3-7: shift

for convenience:
- space+dots 2-5-7: control+shift
space+dots 3-6-7: alt+shift

For example:
type space+dots 3-7, space+dots 3-6, dots 3-4-5 (s) to move to the status tray. Alternatively, press space+dots 3-6-7, dots 3-4-5 (s).

It is now possible to perform common commands like alt+f, ctrl+1-9, and more.

Chorded key mappings:
space+dot 7: backspace
space+dots 3-5: tab
space+dots 1-3-5-6: escape
space+dots 4-6: enter
These set of commands do not require a incremental modifier be pressed previously.

TEST=invoke various modifiers
ctrl+l, alt+f, ctrl+t, alt+shift+l, and more. Verify the expected action occurs.
In addition, use chorded commands such as tab, escape, shift+tab (mixture of the two types above). Verify expected action occurs.

BUG= 707940 , 707937 
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2817313002
Cr-Commit-Position: refs/heads/master@{#464984}

[modify] https://crrev.com/566a5a2b7579c276d818914b2f30688960c3aa98/chrome/browser/resources/chromeos/chromevox/BUILD.gn
[add] https://crrev.com/566a5a2b7579c276d818914b2f30688960c3aa98/chrome/browser/resources/chromeos/chromevox/braille/braille_key_event_rewriter.js
[modify] https://crrev.com/566a5a2b7579c276d818914b2f30688960c3aa98/chrome/browser/resources/chromeos/chromevox/braille/braille_key_types.js
[modify] https://crrev.com/566a5a2b7579c276d818914b2f30688960c3aa98/chrome/browser/resources/chromeos/chromevox/braille/liblouis_test.extjs
[modify] https://crrev.com/566a5a2b7579c276d818914b2f30688960c3aa98/chrome/browser/resources/chromeos/chromevox/host/chrome/braille_background.js
[modify] https://crrev.com/566a5a2b7579c276d818914b2f30688960c3aa98/chrome/browser/resources/chromeos/chromevox/tools/jscompilerwrapper.py

To lpalmaro for documenation. Thanks.

Laura, does something else need to be done here re: #2?

Nope, all good here

Pramod tried this before #4 and was able to use these commands.