gpu: Empty swaps for surfaceless output surfaces.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index b34e6909a82681ff189bf3e9dd063074748a2a8b..86071a0d6ce8b1542207761fd8b15f3bca2e2b26 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -3592,10 +3592,6 @@ bool GLES2DecoderImpl::Initialize(
   }
 
   supports_post_sub_buffer_ = surface->SupportsPostSubBuffer();
-  if (workarounds()
-          .disable_post_sub_buffers_for_onscreen_surfaces &&
-      !surface->IsOffscreen())
-    supports_post_sub_buffer_ = false;
 
   supports_swap_buffers_with_bounds_ = surface->SupportsSwapBuffersWithBounds();
 
@@ -3816,6 +3812,10 @@ Capabilities GLES2DecoderImpl::GetCapabilities() {
       !workarounds().disable_software_to_accelerated_canvas_upgrade;
   caps.emulate_rgb_buffer_with_rgba =
       workarounds().disable_gl_rgb_format;
+  if (workarounds().disable_post_sub_buffers_for_onscreen_surfaces &&
+      !surface_->IsOffscreen()) {

[jbauman, 2017/04/20 21:30:06]

We need a different workaround for this. Otherwise we'll enable empty partial
swap on mesa and virtualbox, where it's probably buggy.

[reveman, 2017/04/20 22:11:40]

Unlikely that we do empty swaps without overlays but still makes sense to have a
separate workaround to be safe. Done.

+    caps.disable_non_empty_post_sub_buffers = true;
+  }
 
   return caps;
 }