Introduce GpuVideoDecodeAcceleratorFactory.

content/public/common/gpu_video_decode_accelerator_helpers.h

+// 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 CONTENT_PUBLIC_COMMON_GPU_VIDEO_DECODE_ACCELERATOR_HELPERS_H_
+#define CONTENT_PUBLIC_COMMON_GPU_VIDEO_DECODE_ACCELERATOR_HELPERS_H_
+
+#include "base/callback.h"
+#include "base/memory/weak_ptr.h"
+
+namespace gfx {
+class GLContext;
+}
+
+namespace gl {
+class GLImage;
+}
+
+namespace gpu {
+namespace gles2 {
+class GLES2Decoder;
+}
+}
+
+namespace content {
+
+// Helpers/defines for specific VideoDecodeAccelerator implementations in GPU
+// process. Which callbacks are required depends on the implementation.
+//
+// Note that these callbacks may be called more than once, and so must own/share
+// ownership of any objects bound to them.
+//
+// Unless specified otherwise, these callbacks must be executed on the GPU Child
+// thread (i.e. the thread which the VDAs are initialized on).
+namespace gpu_vda {

[jam, 2016/03/15 18:25:38]

remove gpu_vda namespace. all code in content is supposed to be just in
"content" namespace only.

+  // Return current GLContext.

[jam, 2016/03/15 18:25:38]

this and the other comments below are confusing. i'd expect these comments on
the methods that take them as a parameter. in isolation seeing the callback,
they don't make much sense.

usually we put these callback typedefs right above the method that takes them as
a parameter. in this case, it would be in gpu_video_decode_accelerator_factory.h

+  using GetGLContextCallback = base::Callback<gfx::GLContext*(void)>;
+
+  // Make the applicable GL context current. To be called by VDAs before
+  // executing any GL calls. Return true on success, false otherwise.
+  using MakeGLContextCurrentCallback = base::Callback<bool(void)>;
+
+  // Bind |image| to |client_texture_id| given |texture_target|.
+  // Return true on success, false otherwise.
+  using BindGLImageCallback =
+      base::Callback<bool(uint32_t client_texture_id,
+                          uint32_t texture_target,
+                          const scoped_refptr<gl::GLImage>& image)>;
+
+  // Return a WeakPtr to a GLES2Decoder, if one is available.
+  using GetGLES2DecoderCallback =
+      base::Callback<base::WeakPtr<gpu::gles2::GLES2Decoder>(void)>;
+}  // namespace gpu_vda
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_COMMON_GPU_VIDEO_DECODE_ACCELERATOR_HELPERS_H_