Revert of Remove unsafe cast from ImageTransportSurfaceOverlayMac::ScheduleCALayer.

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 3b244e3e94bbfe9f521e6b8949c7cca16170c631..4d7b64f32dca242ae52fd5216e03cf61f081ddba 100644
--- a/ui/gl/gl_image_io_surface.mm
+++ b/ui/gl/gl_image_io_surface.mm
@@ -376,22 +376,10 @@
   return cv_pixel_buffer_;
 }
 
-GLImage::Type GLImageIOSurface::GetType() const {
-  return Type::IOSURFACE;
-}
-
 // static
 unsigned GLImageIOSurface::GetInternalFormatForTesting(
     gfx::BufferFormat format) {
   DCHECK(ValidFormat(format));
   return TextureFormat(format);
 }
-
-// static
-GLImageIOSurface* GLImageIOSurface::FromGLImage(GLImage* image) {
-  if (!image || image->GetType() != Type::IOSURFACE)
-    return nullptr;
-  return static_cast<GLImageIOSurface*>(image);
-}
-
 }  // namespace gl