[Blink] Add CHECK for composited layers with nullptr properties

This CL is for debugging the root cause of https://crbug.com/856818 .
Instead of propagating the bad state and crash later, we will abort when
the bad state is assigned, in hope to collect more context from the
crash trace.

BUG=856818

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I41bfa2946396f157f72b79d867dc4717c926169a
Reviewed-on: https://chromium-review.googlesource.com/1168135Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Tien-Ren Chen <trchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582048}

third_party/blink/renderer/platform/graphics/graphics_layer.cc

@@ -1005,6 +1005,9 @@ void GraphicsLayer::SetLayerState(const PropertyTreeState& layer_state,
   }
   layer_state_->state = layer_state;
   layer_state_->offset = layer_offset;
+
+  CHECK(layer_state_->state.Transform() && layer_state_->state.Clip() &&
+        layer_state_->state.Effect());
 }
 
 void GraphicsLayer::SetContentsLayerState(const PropertyTreeState& layer_state,