Use IDCompositionSurface to implement DirectCompositionSurfaceWin.

cc/output/direct_renderer.cc

Index: cc/output/direct_renderer.cc
diff --git a/cc/output/direct_renderer.cc b/cc/output/direct_renderer.cc
index 3b88d774b9483690f05f38855270d037dd31c818..3d371f78047e6ec6522bfec701dfb56db9502820 100644
--- a/cc/output/direct_renderer.cc
+++ b/cc/output/direct_renderer.cc
@@ -88,6 +88,11 @@ void DirectRenderer::Initialize() {
       context_provider->ContextCapabilities().commit_overlay_planes)
     allow_empty_swap_ = true;
 
+  if (context_provider &&
+      context_provider->ContextCapabilities().set_draw_rectangle) {

[danakj, 2017/02/15 16:01:01]

nit: no {}, or merge this with the conditions above so we only check
|context_provider| once

+    use_set_draw_rectangle_ = true;
+  }
+
   initialized_ = true;
 }
 
@@ -510,10 +515,11 @@ void DirectRenderer::DrawRenderPass(const RenderPass* render_pass) {
         current_frame()->ComputeScissorRectForRenderPass());
   }
 
-  bool render_pass_is_clipped =
-      !render_pass_scissor_in_draw_space.Contains(surface_rect_in_draw_space);
   bool is_root_render_pass =
       current_frame()->current_render_pass == current_frame()->root_render_pass;
+  bool render_pass_is_clipped =

[danakj, 2017/02/15 16:01:01]

Can you explain why use_set_draw_rectangle_ implies that we must use a clip rect
even if it contains the surface rect, in a comment here? And how this relates to
the fact that we actually use the damage rect as the draw rectangle?

+      (use_set_draw_rectangle_ && is_root_render_pass) ||
+      !render_pass_scissor_in_draw_space.Contains(surface_rect_in_draw_space);
   bool has_external_stencil_test =
       is_root_render_pass && output_surface_->HasExternalStencilTest();
   bool should_clear_surface =
@@ -582,9 +588,12 @@ void DirectRenderer::DrawRenderPass(const RenderPass* render_pass) {
 
 bool DirectRenderer::UseRenderPass(const RenderPass* render_pass) {
   current_frame()->current_render_pass = render_pass;
-  current_frame()->current_texture = NULL;
+  current_frame()->current_texture = nullptr;
   if (render_pass == current_frame()->root_render_pass) {
     BindFramebufferToOutputSurface();
+
+    if (use_set_draw_rectangle_)
+      output_surface_->SetDrawRectangle(current_frame()->root_damage_rect);
     InitializeViewport(current_frame(), render_pass->output_rect,
                        gfx::Rect(current_frame()->device_viewport_size),
                        current_frame()->device_viewport_size);