Clean up Mac swap acknowledgement code

content/browser/compositor/gpu_browser_compositor_output_surface.cc

Index: content/browser/compositor/gpu_browser_compositor_output_surface.cc
diff --git a/content/browser/compositor/gpu_browser_compositor_output_surface.cc b/content/browser/compositor/gpu_browser_compositor_output_surface.cc
index 70725a2a8b09fb95c329e8846dd5b4edc056d989..c65ba7375874ed6cb2114774bbf4c9382b81670f 100644
--- a/content/browser/compositor/gpu_browser_compositor_output_surface.cc
+++ b/content/browser/compositor/gpu_browser_compositor_output_surface.cc
@@ -28,9 +28,9 @@ GpuBrowserCompositorOutputSurface::GpuBrowserCompositorOutputSurface(
 #if defined(OS_MACOSX)
       should_show_frames_state_(SHOULD_SHOW_FRAMES),
 #endif
-      swap_buffers_completion_callback_(
-          base::Bind(&GpuBrowserCompositorOutputSurface::OnSwapBuffersCompleted,
-                     base::Unretained(this))),
+      swap_buffers_completion_callback_(base::Bind(
+          &GpuBrowserCompositorOutputSurface::OnGpuSwapBuffersCompleted,
+          base::Unretained(this))),
       update_vsync_parameters_callback_(base::Bind(
           &BrowserCompositorOutputSurface::OnUpdateVSyncParametersFromGpu,
           base::Unretained(this))) {
@@ -106,24 +106,14 @@ void GpuBrowserCompositorOutputSurface::SwapBuffers(
 #endif
 }
 
-void GpuBrowserCompositorOutputSurface::OnSwapBuffersCompleted(
+void GpuBrowserCompositorOutputSurface::OnGpuSwapBuffersCompleted(
     const std::vector<ui::LatencyInfo>& latency_info,
     gfx::SwapResult result) {
-#if defined(OS_MACOSX)
-  // On Mac, delay acknowledging the swap to the output surface client until
-  // it has been drawn, see OnSurfaceDisplayed();
-  NOTREACHED();
-#else
   RenderWidgetHostImpl::CompositorFrameDrawn(latency_info);
   OnSwapBuffersComplete();
-#endif
 }
 
 #if defined(OS_MACOSX)
-void GpuBrowserCompositorOutputSurface::OnSurfaceDisplayed() {
-  cc::OutputSurface::OnSwapBuffersComplete();
-}
-
 void GpuBrowserCompositorOutputSurface::SetSurfaceSuspendedForRecycle(
     bool suspended) {
   if (suspended) {