GitLab

This reverts commit a270ee75.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Add aura::WindowOcclusionTracker.
> 
> aura::WindowOcclusionTracker notifies interested windows
> when their occlusion state change.
> 
> This will be used to release resources and throttle execution
> of occluded tabs.
> 
> Time to recompute occlusion on a Samsung Chromebook Pro:
>  100 partially occluded windows*: 108us
>  50 partially occluded windows*: 50us
> * window 0 at position (x=0;y=0), window 1 at position (x=1;y=1),
>   window 2 at position (x=2;y=2), etc.
> Benchmark code:
> https://chromium-review.googlesource.com/c/chromium/src/+/718979
> 
> 
> Bug: 738387
> Change-Id: I65e9e3eb58461e14eda280a133f0acb23a9f1c40
> Reviewed-on: https://chromium-review.googlesource.com/679206
> Commit-Queue: François Doray <fdoray@chromium.org>
> Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#516293}

TBR=sadrul@chromium.org,fdoray@chromium.org

Change-Id: Ib9d0056b520f8fef13d97f0736dbde197c14882d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 784879
Reviewed-on: https://chromium-review.googlesource.com/768168Reviewed-by: Luna Lu <loonybear@chromium.org>
Commit-Queue: Luna Lu <loonybear@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516311}