html-escape screenreader text in Edit Sections dialog

test plan:
 0. create a course section that contains a script, e.g.
    <script>alert('hello')</script>
 1. on the course People page, click the gear menu next to a user
    and select "Edit Sections"
 2. find the section name in the list
 3. ensure the script doesn't run when you click the section

fixes CNVS-17450

Change-Id: I177dbcc06c2105a2b3af2b293060df71533aaf5a
Reviewed-on: https://gerrit.instructure.com/45836
Reviewed-by: Clay Diffrient <cdiffrient@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>
speedgrader: pure css layout

Getting rid of resizeFullHeight() improves performance and makes
reactification easier.

Test plan:
  * In speedgrader, make the discussion and/or submission files lists
    long enough to cause the right sidebar to scroll (for more than one
    student)
  * All the sidebar stuff should still work
  * Nothing should be very bad

Change-Id: I26e852feef41434c203ba14f7f599eba44db7af7
Reviewed-on: https://gerrit.instructure.com/44702
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Chris Hart <chart@instructure.com>
Reviewed-by: Josh Simpson <jsimpson@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Cameron Matheson <cameron@instructure.com>
invalidate stream_item_instances during destroy_stream_items

shouldn't enqueue more jobs while we're already running
destroy_stream_items

Change-Id: Iad9a738d3d1ba9fb793c99acd6a5bef10ae02cb5
Reviewed-on: https://gerrit.instructure.com/45857
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>