ozone: Implement zero/one-copy texture for Ozone GBM.

content/common/gpu/client/gpu_memory_buffer_impl_ozone_native_pixmap.cc

 // Copyright 2014 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 "content/common/gpu/client/gpu_memory_buffer_impl_ozone_native_pixmap.h"
 
 #include "ui/ozone/public/client_native_pixmap_factory.h"
 #include "ui/ozone/public/surface_factory_ozone.h"
 
 namespace content {
@@ skipping 18 matching lines @@
     const DestructionCallback& callback) {
   scoped_ptr<ui::ClientNativePixmap> native_pixmap =
       ui::ClientNativePixmapFactory::GetInstance()->ImportFromHandle(
           handle.native_pixmap_handle, size, format, usage);
   return make_scoped_ptr<GpuMemoryBufferImpl>(
       new GpuMemoryBufferImplOzoneNativePixmap(handle.id, size, format,
                                                callback, native_pixmap.Pass()));
 }
 
 bool GpuMemoryBufferImplOzoneNativePixmap::Map(void** data) {
-  return pixmap_->Map(data);
+  DCHECK(!mapped_);

[reveman, 2015/08/07 17:59:44]

Looks like you already have this dcheck in the pixmap implementation. Why are
you also adding it here? One dcheck is enough.

[dshwang, 2015/08/11 17:44:56]

All GpuMemoryBufferImplXXX::Map/Unmap has same dcheck, so it's a bit weird that
only this doesn't have the dcheck.
On the other hands, I'm reluctant to remove dcheck in
ClientNativePixmapVgem::Map/Unmap because the dcheck helps to understand code.

[reveman, 2015/08/11 18:53:52]

Other implementations have DCHECKs as we're not in control over the API they are
calling into and can make sure they crash in a reliable way when used
inappropriately. We're in control over the ClientNativePixmap API and able to
make sure that inappropriate use is handled correctly. I don't think DCHECKs
here are needed here for that reason.

[dshwang, 2015/08/11 19:36:06]

Done. Thank you for patient explanation.

+  bool result = pixmap_->Map(data);
+  if (result)
+    mapped_ = true;
+  return result;
 }
 
 void GpuMemoryBufferImplOzoneNativePixmap::Unmap() {
+  DCHECK(mapped_);
   pixmap_->Unmap();
+  mapped_ = false;
 }
 
 void GpuMemoryBufferImplOzoneNativePixmap::GetStride(int* stride) const {
   pixmap_->GetStride(stride);
 }
 
 gfx::GpuMemoryBufferHandle GpuMemoryBufferImplOzoneNativePixmap::GetHandle()
     const {
   gfx::GpuMemoryBufferHandle handle;
   handle.type = gfx::OZONE_NATIVE_PIXMAP;
   handle.id = id_;
   return handle;
 }
 
 }  // namespace content