ui: Add out-of-line copy ctors for complex classes.

ui/gl/gl_surface_overlay.cc

 // Copyright 2015 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_surface_overlay.h"
 
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/overlay_transform.h"
 #include "ui/gl/gl_image.h"
 
 namespace gfx {
 
 GLSurfaceOverlay::GLSurfaceOverlay(int z_order,
                                    OverlayTransform transform,
                                    gl::GLImage* image,
                                    const Rect& bounds_rect,
                                    const RectF& crop_rect)
     : z_order_(z_order),
       transform_(transform),
       image_(image),
       bounds_rect_(bounds_rect),
       crop_rect_(crop_rect) {}
 
+GLSurfaceOverlay::GLSurfaceOverlay(const GLSurfaceOverlay& other) = default;
+
 GLSurfaceOverlay::~GLSurfaceOverlay() {}
 
 bool GLSurfaceOverlay::ScheduleOverlayPlane(AcceleratedWidget widget) const {
   return image_->ScheduleOverlayPlane(widget, z_order_, transform_,
                                       bounds_rect_, crop_rect_);
 }
 
 }  // namespace gfx