Route D3D VSync signal to Compositor

content/browser/compositor/gpu_browser_compositor_output_surface.cc

 // Copyright 2014 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 "content/browser/compositor/gpu_browser_compositor_output_surface.h"
 
 #include <utility>
 
 #include "build/build_config.h"
 #include "cc/output/output_surface_client.h"
@@ skipping 26 matching lines @@
   // TODO(reveman): Check context as there's no guarantee we support this
   // even if we request it.
   capabilities_.supports_stencil = support_stencil;
 }
 
 GpuBrowserCompositorOutputSurface::~GpuBrowserCompositorOutputSurface() {
   GetCommandBufferProxy()->SetUpdateVSyncParametersCallback(
       UpdateVSyncParametersCallback());
 }
 
+void GpuBrowserCompositorOutputSurface::SetNeedsVSync(bool needs_vsync) {

[enne (OOO), 2017/01/24 21:32:07]

I still think this is a little bit confusing of a name.  Even when this is
false, the command buffer sends (different) vsync info back to the browser.  Do
you have some way of differentiating this "needs vsync" from the general "needs
vsync"?

Thinking out loud, is this "needs d3d vsync"? Or "needs vsync events" (vs info)?

[stanisc, 2017/01/24 22:22:40]

When D3D VSync feature is enabled that fully replaces the old vsync parameters
mechanism.
On the GPU side VSyncProvider is still invoked but only to get the vsync
interval which on windows comes from WDM, but IPC calls are not triggered by the
old mechanism anymore. We could get rid of the old mechanism entirely if we find
an accurate way to get vsync intervals. We could probably just derive them from
consecutive vsync events but I haven't implemented that yet.

+#if defined(OS_WIN)
+  GetCommandBufferProxy()->SetNeedsVSync(needs_vsync);
+#else
+  NOTREACHED();
+#endif  // defined(OS_WIN)
+}
+
 void GpuBrowserCompositorOutputSurface::OnGpuSwapBuffersCompleted(
     const std::vector<ui::LatencyInfo>& latency_info,
     gfx::SwapResult result,
     const gpu::GpuProcessHostedCALayerTreeParamsMac* params_mac) {
   RenderWidgetHostImpl::CompositorFrameDrawn(latency_info);
   client_->DidReceiveSwapBuffersAck();
 }
 
 void GpuBrowserCompositorOutputSurface::OnReflectorChanged() {
   if (!reflector_) {
@@ skipping 85 matching lines @@
 GpuBrowserCompositorOutputSurface::GetCommandBufferProxy() {
   ui::ContextProviderCommandBuffer* provider_command_buffer =
       static_cast<ui::ContextProviderCommandBuffer*>(context_provider_.get());
   gpu::CommandBufferProxyImpl* command_buffer_proxy =
       provider_command_buffer->GetCommandBufferProxy();
   DCHECK(command_buffer_proxy);
   return command_buffer_proxy;
 }
 
 }  // namespace content