Issue 793949  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0c0f37953a732bd7876d209fa81847eab29abb59

commit 0c0f37953a732bd7876d209fa81847eab29abb59
Author: Katie Dektar <katydek@google.com>
Date: Mon Dec 18 18:35:33 2017

Use an EventRewriter to ensure Select-to-Speak always gets key events.

The EventRewriter is able to get events before they are even passed to
the system menus, which allows Select-to-Speak to have a chance to
process key events before the menus can stop key event propagation.

This change basically refactors select_to_speak_event_handler* to
select_to_speak_event_rewriter*. It neither adds nor removes tests.

Bug:  791809 , 793950 
Change-Id: Ied4c937e0ff1bcb2c56121f048d185290f4a168e
Reviewed-on: https://chromium-review.googlesource.com/823280
Commit-Queue: Katie D <katie@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524748}
[modify] https://crrev.com/0c0f37953a732bd7876d209fa81847eab29abb59/chrome/browser/chromeos/BUILD.gn
[modify] https://crrev.com/0c0f37953a732bd7876d209fa81847eab29abb59/chrome/browser/chromeos/accessibility/accessibility_manager.cc
[modify] https://crrev.com/0c0f37953a732bd7876d209fa81847eab29abb59/chrome/browser/chromeos/accessibility/accessibility_manager.h
[delete] https://crrev.com/40f1f1b0b1e0f44d7976cb36297076073a066124/chrome/browser/chromeos/accessibility/select_to_speak_event_handler.cc
[delete] https://crrev.com/40f1f1b0b1e0f44d7976cb36297076073a066124/chrome/browser/chromeos/accessibility/select_to_speak_event_handler.h
[add] https://crrev.com/0c0f37953a732bd7876d209fa81847eab29abb59/chrome/browser/chromeos/accessibility/select_to_speak_event_rewriter.cc
[add] https://crrev.com/0c0f37953a732bd7876d209fa81847eab29abb59/chrome/browser/chromeos/accessibility/select_to_speak_event_rewriter.h
[rename] https://crrev.com/0c0f37953a732bd7876d209fa81847eab29abb59/chrome/browser/chromeos/accessibility/select_to_speak_event_rewriter_unittest.cc
[modify] https://crrev.com/0c0f37953a732bd7876d209fa81847eab29abb59/chrome/browser/chromeos/chrome_browser_main_chromeos.cc

Moving from just having STS label to also having the UI>Accessibility>SelectToSpeak component to make searching easier in the future. 

Google Chrome	68.0.3440.15 (Official Build) dev (64-bit)
Firmware Version Google_Lulu.6301.136.57

Tested in non-corp account using Google Play Music app
Steps:
Use STS to highlight several times on areas where scrolling could occur, checking for scrolling during highlighting 

Behaved as expected with no scrolling