viz: Remove DCHECK for occlusion in content spcae

Initially this DCHECK was placed to prevent an increase in case #3,
checking quads against the target space occluding region. This case is
not a particularly high cost computation and is still relatively
uncommon.

The occluder in conentspace region may be empty if the target space
occluding rect is reduced to 0 after mapping into content space.

Bug: 1051922
Bug: 1051566
Change-Id: Iffd3433a7bf38be9951479c0d8d4c0d5f2b93dde
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2053410Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Commit-Queue: Daniele Castagna <dcastagna@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741218}

components/viz/service/display/display.cc

@@ -968,7 +968,6 @@ void Display::RemoveOverdrawQuads(CompositorFrame* frame) {
                   SafeConvertRectForRegion(rect_in_content));
             }
           }
-          DCHECK(!occlusion_in_quad_content_space.IsEmpty());
         }
       }