Revert of Mac Overlays: Add GPU back-pressure

ui/gl/gl_image_io_surface.mm

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gl/gl_image_io_surface.h"
 
 #include <map>
 
 #include "base/lazy_instance.h"
 #include "base/mac/foundation_util.h"
@@ skipping 181 matching lines @@
                                        const Point& offset,
                                        const Rect& rect) {
   return false;
 }
 
 bool GLImageIOSurface::ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                             int z_order,
                                             OverlayTransform transform,
                                             const Rect& bounds_rect,
                                             const RectF& crop_rect) {
-  NOTREACHED();
-  return false;
-}
+  // 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);
 
-base::ScopedCFTypeRef<IOSurfaceRef> GLImageIOSurface::io_surface() {
-  return io_surface_;
+  // 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
 void GLImageIOSurface::SetLayerForWidget(
     gfx::AcceleratedWidget widget, CALayer* layer) {
   if (layer)
     g_widget_to_layer_map.Pointer()->insert(std::make_pair(widget, layer));
   else
     g_widget_to_layer_map.Pointer()->erase(widget);
 }
 
 }  // namespace gfx