Improve support for text selection

[johnwarne]

Description

When attempting to add the next/previous word to your currently selected text on a Mac with shift-option-right or shift-option-left, no text is added to your selection.

Steps to Reproduce

1. Select any bit of text on a page.
2. Type shift-option-right or shift-option-left to try to add the next/previous word to your selection.

Actual result:

No text is added.

Expected result:

If typing shift-option-right the next word should be added to your selection. If typing shift-option-left the previous word should be added to your selection.

Reproduces how often:

Easily reproduced

Brave version (brave://version info)

Brave | 0.61.52 Chromium: 73.0.3683.86 (Official Build) (64-bit)
Revision | f9b0bec6063ea50ce2b71f5b9abbae7beee319a6-refs/branch-heads/3683@{#858}
OS | Mac OS X

Reproducible on current release:

• I have not tried to reproduce on brave-browser dev/beta builds

Website problems only:

• The issue does not resolve itself when disabling Brave Shields
• The issue is not reproducible on the latest version of Chrome