Use mojo typemap to simplify the code using DmabufPlane

components/arc/video_accelerator/video_accelerator_struct_traits.h

Index: components/arc/video_accelerator/video_accelerator_struct_traits.h
diff --git a/components/arc/video_accelerator/video_accelerator_struct_traits.h b/components/arc/video_accelerator/video_accelerator_struct_traits.h
new file mode 100644
index 0000000000000000000000000000000000000000..6d49e5dc65e42cc8ac230939d168d2eb25d3758b
--- /dev/null
+++ b/components/arc/video_accelerator/video_accelerator_struct_traits.h
@@ -0,0 +1,38 @@
+// Copyright 2016 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.
+
+#ifndef COMPONENT_ARC_COMMON_VIDEO_ACCELERATOR_STRUCT_TRAITS_H_
+#define COMPONENT_ARC_COMMON_VIDEO_ACCELERATOR_STRUCT_TRAITS_H_
+
+#include "components/arc/common/video_accelerator.mojom.h"
+#include "components/arc/video_accelerator/video_accelerator.h"
+
+namespace mojo {
+
+template <>
+struct StructTraits<arc::mojom::ArcVideoAcceleratorDmabufPlaneDataView,
+                    arc::ArcVideoAcceleratorDmabufPlane> {
+  static uint32_t offset(const arc::ArcVideoAcceleratorDmabufPlane& r) {
+    return r.offset;

[dcheng, 2016/12/01 01:30:50]

Perhaps DCHECK(r.offset > 0)

[yoshiki, 2016/12/06 16:48:34]

I believe this can be 0. Added DCHECK(r.offset >= 0).

+  }
+  static uint32_t stride(const arc::ArcVideoAcceleratorDmabufPlane& r) {

[Luis Héctor Chávez, 2016/11/30 17:57:01]

nit: blank line before, for consistency.

[yoshiki, 2016/12/06 16:48:34]

Done.

+    return r.stride;

[dcheng, 2016/12/01 01:30:50]

Ditto

[yoshiki, 2016/12/06 16:48:34]

Done.

+  }
+
+  static bool Read(arc::mojom::ArcVideoAcceleratorDmabufPlaneDataView data,
+                   arc::ArcVideoAcceleratorDmabufPlane* out) {
+    if (data.offset() < 0 || data.stride() < 0) {

[dcheng, 2016/12/01 01:30:50]

Nit: please out-of-line this to a .cc file

[yoshiki, 2016/12/06 16:48:33]

Done.

+      // Invalid offset/stride.
+      return false;

[Yusuke Sato, 2016/11/30 18:08:34]

qq: How is the false return handled? The original code in
chrome/gpu/gpu_arc_video_service.cc for example does the following:

 273       client_->OnError(	
 274           ::arc::mojom::VideoAcceleratorService::Result::INVALID_ARGUMENT);

Does the same or similar happen? It might be a good idea to add some code
comments for mojo typemap newbies like me.

[dcheng, 2016/12/01 01:30:50]

When StructTraits::Read() returns false, the message fails validation and is
never processed. I believe the message pipe is closed as well.

[Yusuke Sato, 2016/12/01 02:23:08]

Got it, thanks!

+    }
+
+    out->offset = data.offset();
+    out->stride = data.stride();
+    return true;
+  }
+};
+
+}  // namespace arc

[Luis Héctor Chávez, 2016/11/30 17:57:01]

nit: namespace mojo

[yoshiki, 2016/12/06 16:48:34]

Done.

+
+#endif  // COMPONENT_ARC_COMMON_VIDEO_ACCELERATOR_STRUCT_TRAITS_H_