zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

ui/gl/gl_image_io_surface.cc

 // 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 "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
 
 // Note that this must be included after gl_bindings.h to avoid conflicts.
 #include <OpenGL/CGLIOSurface.h>
 
 namespace gfx {
 
 GLImageIOSurface::GLImageIOSurface(const gfx::Size& size) : size_(size) {
 }
 
 GLImageIOSurface::~GLImageIOSurface() {
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!io_surface_);
 }
 
 bool GLImageIOSurface::Initialize(IOSurfaceRef io_surface) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK(!io_surface_);
   io_surface_.reset(io_surface);
   return true;
 }
 
 void GLImageIOSurface::Destroy(bool have_context) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   io_surface_.reset();
 }
 
 gfx::Size GLImageIOSurface::GetSize() { return size_; }
 
 bool GLImageIOSurface::BindTexImage(unsigned target) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   if (target != GL_TEXTURE_RECTANGLE_ARB) {
     // This might be supported in the future. For now, perform strict
     // validation so we know what's going on.
     LOG(ERROR) << "IOSurface requires TEXTURE_RECTANGLE_ARB target";
     return false;
   }
 
   CGLContextObj cgl_context =
       static_cast<CGLContextObj>(GLContext::GetCurrent()->GetHandle());
 
@@ skipping 21 matching lines @@
 
 bool GLImageIOSurface::ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                             int z_order,
                                             OverlayTransform transform,
                                             const Rect& bounds_rect,
                                             const RectF& crop_rect) {
   return false;
 }
 
 }  // namespace gfx