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

gpu/command_buffer/service/gles2_cmd_decoder.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <stdio.h>
 
 #include <algorithm>
 #include <list>
@@ skipping 8215 matching lines @@
 }
 
 error::Error GLES2DecoderImpl::HandleSwapBuffers(
     uint32 immediate_data_size, const gles2::SwapBuffers& c) {
   bool is_offscreen = !!offscreen_target_frame_buffer_.get();
   if (!is_offscreen && surface_->DeferSwapBuffers()) {
     return error::kDeferCommandUntilLater;
   }
 
   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);
   // If offscreen then don't actually SwapBuffers to the display. Just copy
   // the rendered frame to another frame buffer.
   if (is_offscreen) {
     if (offscreen_size_ != offscreen_saved_color_texture_->size()) {
       // Workaround for NVIDIA driver bug on OS X; crbug.com/89557,
       // crbug.com/94163. TODO(kbr): figure out reproduction so Apple will
       // fix this.
@@ skipping 938 matching lines @@
   BindAndApplyTextureParameters(info);
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu