gpu: Empty swaps for surfaceless output surfaces.

content/browser/compositor/gpu_surfaceless_browser_compositor_output_surface.cc

Index: content/browser/compositor/gpu_surfaceless_browser_compositor_output_surface.cc
diff --git a/content/browser/compositor/gpu_surfaceless_browser_compositor_output_surface.cc b/content/browser/compositor/gpu_surfaceless_browser_compositor_output_surface.cc
index e0464b673542e0bb869c817602abb29885aa64ba..3a0e0915ad720f2b683bc4bd1be010346c09acc9 100644
--- a/content/browser/compositor/gpu_surfaceless_browser_compositor_output_surface.cc
+++ b/content/browser/compositor/gpu_surfaceless_browser_compositor_output_surface.cc
@@ -63,7 +63,7 @@ bool GpuSurfacelessBrowserCompositorOutputSurface::IsDisplayedAsOverlayPlane()
 
 unsigned GpuSurfacelessBrowserCompositorOutputSurface::GetOverlayTextureId()
     const {
-  return buffer_queue_->current_texture_id();
+  return buffer_queue_->GetCurrentTextureId();
 }
 
 void GpuSurfacelessBrowserCompositorOutputSurface::SwapBuffers(
@@ -73,8 +73,15 @@ void GpuSurfacelessBrowserCompositorOutputSurface::SwapBuffers(
   // 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));
 }