viz: Allow empty quad visible rect

In Rect::Intersect and throughout the code, when an intersection result
is empty, the origin is thrown away. Which means the resulting Rect may
not be contained in either of the original intersected Rects.

So relax the check in draw_quad and serialization checks to explicitly
allow this.

Fixed: 1095559
Bug: 1072407
Change-Id: I13c9fb9255141466909d99eafba3255d9c7a1c70
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2248162Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#778975}

cc/layers/solid_color_layer_impl.cc

@@ -53,6 +53,9 @@ void SolidColorLayerImpl::AppendSolidQuads(
 
   gfx::Rect visible_quad_rect =
       occlusion_in_layer_space.GetUnoccludedContentRect(visible_layer_rect);
+  if (visible_quad_rect.IsEmpty())
+    return;
+
   auto* quad = render_pass->CreateAndAppendDrawQuad<viz::SolidColorDrawQuad>();
   quad->SetNew(shared_quad_state, visible_layer_rect, visible_quad_rect, color,
                force_anti_aliasing_off);