Mac: Add partial swap support to NSOpenGLContext path

ui/accelerated_widget_mac/io_surface_texture.h

Index: ui/accelerated_widget_mac/io_surface_texture.h
diff --git a/ui/accelerated_widget_mac/io_surface_texture.h b/ui/accelerated_widget_mac/io_surface_texture.h
index 473e69cb4a37475ca67d03a6a684c322b661e263..2cdd235aa1850eaeda7a1aae949e5a80f5523382 100644
--- a/ui/accelerated_widget_mac/io_surface_texture.h
+++ b/ui/accelerated_widget_mac/io_surface_texture.h
@@ -40,7 +40,6 @@ class RenderWidgetHostViewMac;
 class IOSurfaceTexture
     : public base::RefCounted<IOSurfaceTexture> {
  public:
-  // Returns NULL if IOSurfaceTexture or GL API calls fail.
   static scoped_refptr<IOSurfaceTexture> Create(
       bool needs_gl_finish_workaround);
 
@@ -54,6 +53,7 @@ class IOSurfaceTexture
   // larger than the IOSurface, the remaining right and bottom edges will be
   // white. |window_scale_factor| is 1 in normal views, 2 in HiDPI views.
   bool DrawIOSurface() WARN_UNUSED_RESULT;
+  bool DrawIOSurfaceWithDamageRect(gfx::Rect damage_rect) WARN_UNUSED_RESULT;
 
   // Returns true if the offscreen context used by this surface has been
   // poisoned.
@@ -67,6 +67,10 @@ class IOSurfaceTexture
       bool needs_gl_finish_workaround);
   ~IOSurfaceTexture();
 
+  // Draw the sepecified rect of the IOSurface. If |draw_boundary| is true,
+  // clear any overflow regions with white.
+  bool DrawIOSurfaceInternal(gfx::Rect damage_rect, bool draw_boundary);
+
   // Unref the IOSurfaceTexture and delete the associated GL texture. If the GPU
   // process is no longer referencing it, this will delete the IOSurface.
   void ReleaseIOSurfaceAndTexture();