Revert of Mac Overlays: Add GPU back-pressure

ui/gl/gl_image_io_surface.mm

Index: ui/gl/gl_image_io_surface.mm
diff --git a/ui/gl/gl_image_io_surface.mm b/ui/gl/gl_image_io_surface.mm
index b488c533cc49c2a3295e48836499f125dc3d2830..2044f3775a16590370ee323eac853eb007aaf98f 100644
--- a/ui/gl/gl_image_io_surface.mm
+++ b/ui/gl/gl_image_io_surface.mm
@@ -199,12 +199,22 @@
                                             OverlayTransform transform,
                                             const Rect& bounds_rect,
                                             const RectF& crop_rect) {
-  NOTREACHED();
-  return false;
-}
-
-base::ScopedCFTypeRef<IOSurfaceRef> GLImageIOSurface::io_surface() {
-  return io_surface_;
+  // Only simple overlay planes are currently supported.
+  DCHECK_EQ(0, z_order);
+  DCHECK_EQ(gfx::RectF(0, 0, 1, 1).ToString(), crop_rect.ToString());
+  DCHECK_EQ(gfx::OVERLAY_TRANSFORM_NONE, transform);
+
+  // Convert the phony widget to the appropriate CALayer.
+  auto found = g_widget_to_layer_map.Pointer()->find(widget);
+  if (found == g_widget_to_layer_map.Pointer()->end())
+    return false;
+  CALayer* layer = found->second;
+
+  // Also note that transactions are not disabled. The caller must ensure that
+  // all changes to the CALayer tree happen atomically.
+  [layer setContents:static_cast<id>(io_surface_.get())];
+  [layer setFrame:bounds_rect.ToCGRect()];
+  return true;
 }
 
 // static