Aura: Have ui::Layer implement WebKit::WebExternalTextureLayerClient

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 81ecee496c9c70038085eb2f2be1fe5c023cf8ab..ae0ab29e732e9af7efb228a196aa5981ee287ecd 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -8233,11 +8233,6 @@ error::Error GLES2DecoderImpl::HandleSwapBuffers(
   }
 
   int this_frame_number = frame_number_++;
-  // TRACE_EVENT for gpu tests:
-  TRACE_EVENT_INSTANT2("test_gpu", "SwapBuffers",

[jbates, 2012/07/18 22:50:28]

why did this move? it changed the windows WebGL latency results so I don't think
this was correct.

[jonathan.backer, 2012/07/19 13:04:31]

This moved because I had CrOS use a real display for GpuFeatureTests in order to
remove some dead code (http://codereview.chromium.org/10696221/) that was only
being used in test (it used to be used in production, but had been deprecated a
month or two ago).

More specifically, CrOS uses the GPU process to display it's UI. So any time a
window move, a menu opened, or new tab contents need display, we'd trigger a
SwapBuffers in the decoder process. It was clear that GpuFeatureTests only meant
to grab renderer SwapBuffers. Moving this to ImageTransportSurface achieves this
goal.

As for why this affects latency, we're now signalling a SwapBuffers after it has
been acted on, rather than before. Specifically,
PbufferImageTransportSurface::SwapBuffers() defers to a fence before telling the
browser that there is a new frame to display. I'm not sure what you're trying to
measure, but my gut tells me that this is probably what you want --- this fence
introduces latency that is user visible (and a quick search in content/browser/
for "test_gpu" comes up empty for windows, suggesting that it's not accounted
for in some other way).

If this is definitely not what you want, let me know and I can work around it.

-                       "GLImpl", static_cast<int>(gfx::GetGLImplementation()),
-                       "width", (is_offscreen ? offscreen_size_.width() :
-                                 surface_->GetSize().width()));
   TRACE_EVENT2("gpu", "GLES2DecoderImpl::HandleSwapBuffers",
                "offscreen", is_offscreen,
                "frame", this_frame_number);