Use IDCompositionSurface to implement DirectCompositionSurfaceWin.

content/browser/compositor/browser_compositor_output_surface.h

Index: content/browser/compositor/browser_compositor_output_surface.h
diff --git a/content/browser/compositor/browser_compositor_output_surface.h b/content/browser/compositor/browser_compositor_output_surface.h
index 8c8f56cac0d11ffea21a8139a87c82c69e2c536f..391f44d6b92315bdf7546e7ae6bcfb8cdebb8bad 100644
--- a/content/browser/compositor/browser_compositor_output_surface.h
+++ b/content/browser/compositor/browser_compositor_output_surface.h
@@ -35,6 +35,7 @@ class CONTENT_EXPORT BrowserCompositorOutputSurface
   ~BrowserCompositorOutputSurface() override;
 
   // cc::OutputSurface implementation.
+  void SetDrawRectangle(const gfx::Rect& draw_rectangle) override;

[danakj, 2017/02/22 15:04:08]

The GPU subclass overrides this, can you move this empty one to the software
subclass instead so we don't have overrides of a non-abstract method in the GPU
subclass?

   cc::OverlayCandidateValidator* GetOverlayCandidateValidator() const override;
   bool HasExternalStencilTest() const override;
   void ApplyExternalStencil() override;