Mac Overlays: Add sandwich strategy

cc/output/overlay_strategy_underlay.h

Index: cc/output/overlay_strategy_underlay.h
diff --git a/cc/output/overlay_strategy_underlay.h b/cc/output/overlay_strategy_underlay.h
index fd55bef43190f0faf6ca04ae9f2a1887df581192..e3214318f069421379a83500d982ad1689876783 100644
--- a/cc/output/overlay_strategy_underlay.h
+++ b/cc/output/overlay_strategy_underlay.h
@@ -16,15 +16,17 @@ class TextureDrawQuad;
 // for the video quad. The overlay content can then be blended in by the
 // hardware under the the scene. This is only valid for overlay contents that
 // are fully opaque.
-class CC_EXPORT OverlayStrategyUnderlay : public OverlayStrategyCommon {
+class CC_EXPORT OverlayStrategyUnderlay : public OverlayStrategyCommonDelegate {
  public:
-  explicit OverlayStrategyUnderlay(
-      OverlayCandidateValidator* capability_checker);
+  OverlayStrategyUnderlay() {}
+  ~OverlayStrategyUnderlay() override;
+
   bool TryOverlay(OverlayCandidateValidator* capability_checker,
                   RenderPassList* render_passes_in_draw_order,
                   OverlayCandidateList* candidate_list,
                   const OverlayCandidate& candidate,
-                  QuadList::Iterator candidate_iterator) override;
+                  QuadList::Iterator candidate_iterator,
+                  float device_scale_factor) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OverlayStrategyUnderlay);