Mac: Enable partial swap

content/common/gpu/image_transport_surface_overlay_mac.h

Index: content/common/gpu/image_transport_surface_overlay_mac.h
diff --git a/content/common/gpu/image_transport_surface_overlay_mac.h b/content/common/gpu/image_transport_surface_overlay_mac.h
index e4822db21f8e6f7fe35aa1196776cdaf7901e833..62913a096692b2b7001dcb2fbaf202ed521ecbff 100644
--- a/content/common/gpu/image_transport_surface_overlay_mac.h
+++ b/content/common/gpu/image_transport_surface_overlay_mac.h
@@ -65,6 +65,10 @@ class ImageTransportSurfaceOverlayMac : public gfx::GLSurface,
 
     // The size of the full frame, in dip.
     gfx::Size dip_size;
+
+    // If true, the partial damage rect for the frame.
+    bool use_partial_damage;
+    gfx::Rect dip_partial_damage_rect;
   };
 
   ~ImageTransportSurfaceOverlayMac() override;
@@ -82,6 +86,7 @@ class ImageTransportSurfaceOverlayMac : public gfx::GLSurface,
   scoped_ptr<ImageTransportHelper> helper_;
   base::scoped_nsobject<CAContext> ca_context_;
   base::scoped_nsobject<CALayer> layer_;
+  base::scoped_nsobject<CALayer> partial_damage_layer_;
 
   gfx::Size pixel_size_;
   float scale_factor_;
@@ -96,6 +101,10 @@ class ImageTransportSurfaceOverlayMac : public gfx::GLSurface,
   // have not yet been displayed by CheckAndDisplayPendingSwaps.
   std::deque<PendingSwap> pending_swaps_;
 
+  // The union of the damage rects of SwapBuffersInternal since the last
+  // non-partial swap.
+  gfx::Rect accumulated_partial_damage_pixel_rect_;
+
   // The display link used to compute the delay for the posted task in
   // PostCheckAndDisplayPendingSwaps.
   scoped_refptr<ui::DisplayLinkMac> display_link_mac_;