Text selection behavior ignored the highlighted text for backward text selection using left mouse button

Reported in 4345105-zd-woothemes:

> When you mark text by double-clicking on a word and moving your cursor while holding LMB it will select text word by word and it works normally when moving forwards, but when moving backwards it will unmark the word you double-clicked on. I'm not sure if this is a feature or something that was overlooked, but it's not how it works in any other program, making it frustrating to use as a person who for some reason mostly selects text backwards.

### Expected
The user expects that the highlighted text would be selected for backward text selection by holding the left mouse button.

### Observed
The highlighted text is ignored when selecting text by holding the left mouse button and moving it backward. The user observed that this issue doesn't happen on the Notepad++ app.

### Reproduced

1. Double-click on a word in the note.
2. Move the cursor backward while holding the left mouse button
3. Noticed the word selected in Step 1 wasn't highlighted.


### Where did you see the bug
- OS: Windows 10
- App version: 2.19.1

No source file, test, or entry point is named. Reproduce the behavior in the Windows app using the reported double-click and backward left-button drag steps, then verify that the initially highlighted word remains selected and that the forward-selection behavior is unchanged.

Written by the indexing model from the issue text.