Implement the msaa_is_slow and avoid_stencil_buffers gpu capabilities.

These capabitilites were not implemented in the passthrough command decoder
which resulted in poor MSAA performace on Intel high DPI.

BUG=801659
BUG=800133
BUG=800011
BUG=799951

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I2e1f0f3b4b8267421646279b6d3154223f8199b0
Reviewed-on: https://chromium-review.googlesource.com/1024282Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552794}

gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc

@@ -1209,6 +1209,9 @@ gpu::Capabilities GLES2DecoderPassthroughImpl::GetCapabilities() {
   caps.post_sub_buffer = surface_->SupportsPostSubBuffer();
   caps.surfaceless = !offscreen_ && surface_->IsSurfaceless();
   caps.flips_vertically = !offscreen_ && surface_->FlipsVertically();
+  caps.msaa_is_slow = feature_info_->workarounds().msaa_is_slow;
+  caps.avoid_stencil_buffers =
+      feature_info_->workarounds().avoid_stencil_buffers;
   caps.multisample_compatibility =
       feature_info_->feature_flags().ext_multisample_compatibility;
   caps.dc_layers = !offscreen_ && surface_->SupportsDCLayers();