Surface Synchronization: Fix Crash in RenderWidgetHostViewMac

In RenderWidgetHostViewMac::UpdateScreenInfo, it may follow a null
|render_widget_host_| pointer at tear down. This CL adds a null check.

Bug: 783547
Change-Id: Ia83c3f82ea8331c1fa52edaebc4cf88a9a1a20f3
Reviewed-on: https://chromium-review.googlesource.com/767687
Reviewed-by: Saman Sami <samans@chromium.org>
Commit-Queue: Fady Samuel <fsamuel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516107}
1 file changed