GitLab

A crash can result from the following sequence of events (as debugged
by ellyjones):
  1.  displays_require_update_ is false
  2.  The configure timer ticks, ConfigureTimerFired is called
  3.  ConfigureTimerFired -> UpdateDisplaysIfNeeded, which is a noop
      because displays_require_update_ is false
  4.  ConfigureTimerFired -> NotifyDisplaysChanged, which starts
      iterating the list
  5.  One instance of NativeWidgetNSWindowBridge::
      OnDisplayMetricsChanged calls ScreenMac::GetDisplayNearestWindow
  6.  Since the display list has not yet been updated (at step 3), that
      falls back to GetCachedDisplayForScreen (and its call to
      UpdateDisplaysIfNeeded is a noop)
  7.  Since the display list still hasn't been updated,
      GetCachedDisplayForScreen calls OnNSScreensMayHaveChanged, which
      sets displays_require_update_ to true
  8.  The iteration from step 4 resumes, and another instance of
      NativeWidgetNSWindowBridge::OnDisplayMetricsChanged runs
  9.  For *this* instance, displays_require_update_ is true, so
      UpdateDisplaysIfNeeded destroys the old version of displays_
  10. The iteration from step 4 resumes, now iterating on a destroyed
      displays_.

Break this by removing the call to OnNSScreensMayHaveChanged from
GetCachedDisplayForScreen, to see if it removes the crashes.

Bug: 1033866
Change-Id: I1271c83d5456ab9c863969842816661c6b3e0569
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2135312Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756378}