Highlight stops following cursor, even when mouse is down

[sethladd]

I'm using Dart Editor version 0.5.20_r24216 on a Mac.

Please see attached movie. Very odd.

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Attachment:
[highlighting stops.mov](https://storage.googleapis.com/google-code-attachments/dart/issue-11402/comment-0/highlighting stops.mov) (1.25 MB)

[clayberg]

Set owner to @stevemessick.
Added this to the M6 milestone.
Removed Priority-Unassigned label.
Added Priority-Medium label.

[stevemessick]

Added Duplicate label.
Marked as being merged into #2268.