1332302 - Reader View's first-run infopanel is resizable and causes visual artifacts

Status: RESOLVED DUPLICATE of bug 1262211

(Firefox :: Tours, defect)

Description

[Andrei Vaida [:avaida]]

[Affected versions]:
- 50.1.0 (20161205173838)
- 51.0-build2 (20170118123726)
- 51.0b12 (20170105155013)
- 52.0a2 (20170119004006)
- 53.0a1 (20170112030301)

[Affected platforms]:
- Ubuntu 16.04
- Ubuntu 14.04

[Steps to reproduce]:
1. Launch Firefox with a new profile.
2. Access a page that will display the first-run Reader View infopanel.
  (e.g.) http://tinyurl.com/74s2ncq
3. Position your mouse cursor above the infopanel, right on top of the awesomebar.
4. Click and drag from top to bottom.

[Expected result]:
- The user cannot resize the infopanel.

[Actual result]:
- The Reader View infopanel is resizable and visual artifacts are displayed if an attempt is made to do so. Screencast: https://goo.gl/FZdLcn.

[Regression range]:
- Please note that this is _NOT_ a regression. Checking with mozregression, I noticed that the pushlog I've managed to obtain actually contains the bug that implemented the infopane in the first place.
- Last good revision: 7723b15ea695 (2015-05-01)
- First bad revision: 1e8d30cb367e (2015-05-02)
- Pushlog: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=7723b15ea695&tochange=1e8d30cb367e

[Additional notes]:
- This is reproducible on both x86 and x64 Linux build architectures.
- I've managed to reproduce this with different machines, each using a different GPU: an HP ProBook with Intel HD 520, a Desktop PC with Intel HD 5200 and another one with Intel HD 530.
- This is _NOT_ reproducible on Windows and Mac platforms.