fixes the dropdown rendering issue in gradebook
fixes the dropdown rendering issue in gradebook

Chrome 40 introduced a rendering issue that
prevents selection of menu items in dropdowns
on the gradebooks page. This issue is fixed in
Chrome 42 (Canary). This commit should be
reverted when Chrome 40 and 41 are no
longer supported

fixes CNVS-18276

test plan:
- In chrome 40, create a course with 2 sections
  and 1 student
- Go to the gradebook

1. Click on the change sections dropdown
  - Menu should appear without rendering errors
  - Select a menu item
  - Menu should disappear compeltely

2. Click on the change sections dropdown again
  - Menu should appear without rendering errors
  - Click outside of the menu
  - Menu should disappear completely

3. Repeat the two steps above for the settings
   dropdown

4. Check for performance problems in
   gradebooks with a lot of students /
   assignments

Change-Id: I50805ea3bb0f49e0ba943b319c02bed283b5b774
Reviewed-on: https://gerrit.instructure.com/49237
Reviewed-by: Spencer Olson <7cc0890d6f1f70810a023e7173eca5724d6c8e49@instructure.com>
QA-Review: Amber Taniuchi <ef4bfd1e6d278f6bc7d4a478f02be2cb9581a0a5@instructure.com>
Product-Review: Dylan Ross <7374864f039b76a5b01d8407f92828e3f173309e@instructure.com>
Tested-by: Jenkins
Reviewed-by: Josh Simpson <bfb4987b134a00f73d881fff5113b1d5fa1876bc@instructure.com>

sdeleon28/canvas-lms,redconfetti/canvas-lms,fronteerio/canvas-lms,redconfetti/canvas-lms,va7map/canvas-lms,tgroshon/canvas-lms,Jyaasa/canvas-lms,antoniuslin/canvas-lms,tgroshon/canvas-lms,kyroskoh/canvas-lms,venturehive/canvas-lms,leftplusrightllc/canvas-lms,jay3126/canvas-lms,tgroshon/canvas-lms,utkarshx/canvas-lms,Rvor/canvas-lms,antoniuslin/canvas-lms,jay3126/canvas-lms,leftplusrightllc/canvas-lms,SwinburneOnline/canvas-lms,kyroskoh/canvas-lms,skmezanul/canvas-lms,samuels410/greatlakes-lms,ShreniiNepal/shrenii_lmp,juoni/canvas-lms,va7map/canvas-lms,grahamb/canvas-lms,jay3126/canvas-lms,kyroskoh/canvas-lms,sfu/canvas-lms,samuels410/greatlakes-lms,shidao-fm/canvas-lms,djbender/canvas-lms,efrj/canvas-lms,roxolan/canvas-lms,roxolan/canvas-lms,kyroskoh/canvas-lms,leftplusrightllc/canvas-lms,sfu/canvas-lms,Rvor/canvas-lms,fronteerio/canvas-lms,juoni/canvas-lms,whalejasmine/canvas-lms,wrdsb/canvas-lms,efrj/canvas-lms,ShreniiNepal/shrenii_lmp,HotChalk/canvas-lms,antoniuslin/canvas-lms,whalejasmine/canvas-lms,grahamb/canvas-lms,tgroshon/canvas-lms,sfu/canvas-lms,whalejasmine/canvas-lms,fronteerio/canvas-lms,HotChalk/canvas-lms,shidao-fm/canvas-lms,jay3126/canvas-lms,juoni/canvas-lms,greyhwndz/canvas-lms,juoni/canvas-lms,efrj/canvas-lms,ShreniiNepal/shrenii_lmp,grahamb/canvas-lms,greyhwndz/canvas-lms,venturehive/canvas-lms,venturehive/canvas-lms,skmezanul/canvas-lms,whalejasmine/canvas-lms,samuels410/greatlakes-lms,utkarshx/canvas-lms,wrdsb/canvas-lms,greyhwndz/canvas-lms,sfu/canvas-lms,Jyaasa/canvas-lms,HotChalk/canvas-lms,va7map/canvas-lms,Rvor/canvas-lms,antoniuslin/canvas-lms,sfu/canvas-lms,skmezanul/canvas-lms,shidao-fm/canvas-lms,ShreniiNepal/shrenii_lmp,SwinburneOnline/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,efrj/canvas-lms,HotChalk/canvas-lms,skmezanul/canvas-lms,roxolan/canvas-lms,redconfetti/canvas-lms,SwinburneOnline/canvas-lms,shidao-fm/canvas-lms,greyhwndz/canvas-lms,redconfetti/canvas-lms,leftplusrightllc/canvas-lms,va7map/canvas-lms,wrdsb/canvas-lms,SwinburneOnline/canvas-lms,djbender/canvas-lms,Jyaasa/canvas-lms,sfu/canvas-lms,samuels410/greatlakes-lms,djbender/canvas-lms,sdeleon28/canvas-lms,sdeleon28/canvas-lms,sdeleon28/canvas-lms,utkarshx/canvas-lms,djbender/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,wrdsb/canvas-lms,grahamb/canvas-lms,Rvor/canvas-lms,Jyaasa/canvas-lms,utkarshx/canvas-lms,venturehive/canvas-lms