Surface Synchronization: Convert invariants violations to DCHECKs

This CL converts some not so useful CHECKs in AsyncLayerTreeFrameSink
into DCHECKs that can be caught in debug builds by developers.

We would like to merge this CL into M69 as well to eliminate a source
of renderer crashes.

Bug: 871450
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I235d068ea72774b020ba7a241507d0f4201d8dc0
Reviewed-on: https://chromium-review.googlesource.com/1181766Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Fady Samuel <fsamuel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584560}

cc/mojo_embedder/async_layer_tree_frame_sink.cc

@@ -133,11 +133,11 @@ void AsyncLayerTreeFrameSink::SubmitCompositorFrame(
         local_surface_id_provider_->GetLocalSurfaceIdForFrame(frame);
   } else {
     if (local_surface_id_ == last_submitted_local_surface_id_) {
-      CHECK_EQ(last_submitted_device_scale_factor_,
+      DCHECK_EQ(last_submitted_device_scale_factor_,
                 frame.device_scale_factor());
-      CHECK_EQ(last_submitted_size_in_pixels_.height(),
+      DCHECK_EQ(last_submitted_size_in_pixels_.height(),
                 frame.size_in_pixels().height());
-      CHECK_EQ(last_submitted_size_in_pixels_.width(),
+      DCHECK_EQ(last_submitted_size_in_pixels_.width(),
                 frame.size_in_pixels().width());
     }
   }