gpu: Empty swaps for surfaceless output surfaces.

content/browser/compositor/gpu_surfaceless_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_surfaceless_browser_compositor_output_surface.h"
 
 #include <utility>
 
 #include "cc/output/output_surface_client.h"
 #include "cc/output/output_surface_frame.h"
@@ skipping 45 matching lines @@
     ~GpuSurfacelessBrowserCompositorOutputSurface() {
 }
 
 bool GpuSurfacelessBrowserCompositorOutputSurface::IsDisplayedAsOverlayPlane()
     const {
   return true;
 }
 
 unsigned GpuSurfacelessBrowserCompositorOutputSurface::GetOverlayTextureId()
     const {
-  return buffer_queue_->current_texture_id();
+  return buffer_queue_->GetCurrentTextureId();
 }
 
 void GpuSurfacelessBrowserCompositorOutputSurface::SwapBuffers(
     cc::OutputSurfaceFrame frame) {
   DCHECK(buffer_queue_);
   DCHECK(reshape_size_ == frame.size);
   // TODO(ccameron): What if a swap comes again before OnGpuSwapBuffersCompleted
   // happens, we'd see the wrong swap size there?
   swap_size_ = reshape_size_;
-  buffer_queue_->SwapBuffers(frame.sub_buffer_rect ? *frame.sub_buffer_rect
-                                                   : gfx::Rect(swap_size_));
+
+  gfx::Rect damage_rect =
+      frame.sub_buffer_rect ? *frame.sub_buffer_rect : gfx::Rect(swap_size_);
+  // Use previous buffer when damage rect is empty. This avoids unnecessary
+  // partial swap work and makes it possible to support empty swaps on devices
+  // where partial swaps are disabled.
+  if (!damage_rect.IsEmpty())
+    buffer_queue_->SwapBuffers(damage_rect);
+
   GpuBrowserCompositorOutputSurface::SwapBuffers(std::move(frame));
 }
 
 void GpuSurfacelessBrowserCompositorOutputSurface::BindFramebuffer() {
   DCHECK(buffer_queue_);
   buffer_queue_->BindFramebuffer();
 }
 
 GLenum GpuSurfacelessBrowserCompositorOutputSurface::
     GetFramebufferCopyTextureFormat() {
@@ skipping 26 matching lines @@
     force_swap = true;
   }
   buffer_queue_->PageFlipComplete();
   GpuBrowserCompositorOutputSurface::OnGpuSwapBuffersCompleted(
       latency_info, result, params_mac);
   if (force_swap)
     client_->SetNeedsRedrawRect(gfx::Rect(swap_size_));
 }
 
 }  // namespace content