VDA: document the behavior of calling Reset before NotifyFlushDone.

media/video/video_decode_accelerator.h

 // Copyright (c) 2012 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 MEDIA_VIDEO_VIDEO_DECODE_ACCELERATOR_H_
 #define MEDIA_VIDEO_VIDEO_DECODE_ACCELERATOR_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 268 matching lines @@
   virtual void ReusePictureBuffer(int32_t picture_buffer_id) = 0;
 
   // Flushes the decoder: all pending inputs will be decoded and pictures handed
   // back to the client, followed by NotifyFlushDone() being called on the
   // client.  Can be used to implement "end of stream" notification.
   virtual void Flush() = 0;
 
   // Resets the decoder: all pending inputs are dropped immediately and the
   // decoder returned to a state ready for further Decode()s, followed by
   // NotifyResetDone() being called on the client.  Can be used to implement
-  // "seek".
+  // "seek". After Flush is called, it is OK to call Reset before receiving
+  // NotifyFlushDone() and VDA should cancel the flush. Note NotifyFlushDone()
+  // may be on the way to the client. If client gets NotifyFlushDone(), it
+  // should be before NotifyResetDone().
   virtual void Reset() = 0;
 
   // An optional graphics surface that the VDA should render to. For setting
   // an output SurfaceView on Android. Passing |kNoSurfaceID| will clear any
   // previously set surface in favor of an internally generated texture.
   virtual void SetSurface(int32_t surface_id);
 
   // Destroys the decoder: all pending inputs are dropped immediately and the
   // component is freed.  This call may asynchornously free system resources,
   // but its client-visible effects are synchronous.  After this method returns
@@ skipping 53 matching lines @@
 // std::unique_ptr<VideoDecodeAccelerator> uses "Destroy()" instead of trying to
 // use the destructor.
 template <>
 struct MEDIA_EXPORT default_delete<media::VideoDecodeAccelerator> {
   void operator()(media::VideoDecodeAccelerator* vda) const;
 };
 
 }  // namespace std
 
 #endif  // MEDIA_VIDEO_VIDEO_DECODE_ACCELERATOR_H_