Add offset support to BitstreamBuffer.

content/common/gpu/media/v4l2_video_encode_accelerator.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 <fcntl.h>
 #include <linux/videodev2.h>
 #include <poll.h>
 #include <sys/eventfd.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
@@ skipping 204 matching lines @@
   DVLOG(3) << "UseOutputBitstreamBuffer(): id=" << buffer.id();
   DCHECK(child_task_runner_->BelongsToCurrentThread());
 
   if (buffer.size() < output_buffer_byte_size_) {
     NOTIFY_ERROR(kInvalidArgumentError);
     return;
   }
 
   scoped_ptr<base::SharedMemory> shm(
       new base::SharedMemory(buffer.handle(), false));
-  if (!shm->Map(buffer.size())) {
+  if (!shm->MapAt(buffer.offset(), buffer.size())) {
     NOTIFY_ERROR(kPlatformFailureError);
     return;
   }
 
   scoped_ptr<BitstreamBufferRef> buffer_ref(
       new BitstreamBufferRef(buffer.id(), shm.Pass(), buffer.size()));
   encoder_thread_.message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&V4L2VideoEncodeAccelerator::UseOutputBitstreamBufferTask,
                  base::Unretained(this),
@@ skipping 921 matching lines @@
   reqbufs.count = 0;
   reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE;
   reqbufs.memory = V4L2_MEMORY_MMAP;
   IOCTL_OR_LOG_ERROR(VIDIOC_REQBUFS, &reqbufs);
 
   output_buffer_map_.clear();
   free_output_buffers_.clear();
 }
 
 }  // namespace content