Add diagnostic CHECK for empty output rect in CompositorFrame

This is a temporary CHECK that should help us diagnose
deserialization failures in SubmitCompositorFrame.

Bug: 1022565, 979564
Change-Id: I60da30e82cc39edd791800f4cc2dd0293d05fda1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1913657Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715122}

services/viz/public/cpp/compositing/compositor_frame_mojom_traits.h

@@ -29,7 +29,9 @@ struct StructTraits<viz::mojom::CompositorFrameDataView, viz::CompositorFrame> {
 
   static const viz::RenderPassList& passes(const viz::CompositorFrame& input) {
     DCHECK(!input.render_pass_list.empty());
-    DCHECK(!input.render_pass_list.back()->output_rect.size().IsEmpty());
+    // TODO(samans): Change this back to a DCHECK once we figure out the cause.
+    // https://crbug.com/1022565 https://crbug.com/979564
+    CHECK(!input.render_pass_list.back()->output_rect.size().IsEmpty());
     return input.render_pass_list;
   }