libvpx: Pull from upstream

source/libvpx/vpx/vpx_frame_buffer.h

 /*
  *  Copyright (c) 2014 The WebM project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef VPX_VPX_FRAME_BUFFER_H_
 #define VPX_VPX_FRAME_BUFFER_H_
 
 /*!\file
  * \brief Describes the decoder external frame buffer interface.
  */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #include "./vpx_integer.h"
 
 /*!\brief The maximum number of work buffers used by libvpx.
+ *  Support maximum 4 threads to decode video in parallel.
+ *  Each thread will use one work buffer.
+ * TODO(hkuang): Add support to set number of worker threads dynamically.
  */
-#define VPX_MAXIMUM_WORK_BUFFERS 1
+#define VPX_MAXIMUM_WORK_BUFFERS 8
 
 /*!\brief The maximum number of reference buffers that a VP9 encoder may use.
  */
 #define VP9_MAXIMUM_REF_BUFFERS 8
 
 /*!\brief External frame buffer
  *
  * This structure holds allocated frame buffers used by the decoder.
  */
 typedef struct vpx_codec_frame_buffer {
@@ skipping 34 matching lines @@
  * \param[in] fb           Pointer to vpx_codec_frame_buffer_t
  */
 typedef int (*vpx_release_frame_buffer_cb_fn_t)(
     void *priv, vpx_codec_frame_buffer_t *fb);
 
 #ifdef __cplusplus
 }  // extern "C"
 #endif
 
 #endif  // VPX_VPX_FRAME_BUFFER_H_