Make V4L2CaptureDelegate non-ref-counted

media/capture/video/linux/v4l2_capture_delegate.cc

 // Copyright 2015 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 "media/capture/video/linux/v4l2_capture_delegate.h"
 
 #include <linux/version.h>
 #include <linux/videodev2.h>
 #include <poll.h>
 #include <sys/fcntl.h>
@@ skipping 488 matching lines @@
       0) {
     SetErrorState(FROM_HERE, "VIDIOC_STREAMON failed");
     return;
   }
 
   client_->OnStarted();
   is_capturing_ = true;
 
   // Post task to start fetching frames from v4l2.
   v4l2_task_runner_->PostTask(
-      FROM_HERE, base::Bind(&V4L2CaptureDelegate::DoCapture, this));
+      FROM_HERE,
+      base::Bind(&V4L2CaptureDelegate::DoCapture, base::Unretained(this)));

[mcasas, 2017/04/11 17:17:34]

How would you guarantee that |this| is alive
when this Task gets scheduled, if V4L2CaptureDelegate
is "created and destroyed on the owner's thread" [1]
which is, presumably, different from 
|v4l2_task_runner_| ?

[1]
https://cs.chromium.org/chromium/src/media/capture/video/linux/v4l2_capture_d...

[Chandan, 2017/04/11 19:46:43]

Need to use weak pointer then? What do you suggest?

 }
 
 void V4L2CaptureDelegate::StopAndDeAllocate() {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   // The order is important: stop streaming, clear |buffer_pool_|,
   // thus munmap()ing the v4l2_buffers, and then return them to the OS.
   v4l2_buf_type capture_type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
   if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_STREAMOFF, &capture_type)) <
       0) {
     SetErrorState(FROM_HERE, "VIDIOC_STREAMOFF failed");
@@ skipping 293 matching lines @@
         cb.Run(std::move(blob));
     }
 
     if (HANDLE_EINTR(ioctl(device_fd_.get(), VIDIOC_QBUF, &buffer)) < 0) {
       SetErrorState(FROM_HERE, "Failed to enqueue capture buffer");
       return;
     }
   }
 
   v4l2_task_runner_->PostTask(
-      FROM_HERE, base::Bind(&V4L2CaptureDelegate::DoCapture, this));
+      FROM_HERE,
+      base::Bind(&V4L2CaptureDelegate::DoCapture, base::Unretained(this)));
 }
 
 void V4L2CaptureDelegate::SetErrorState(
     const tracked_objects::Location& from_here,
     const std::string& reason) {
   DCHECK(v4l2_task_runner_->BelongsToCurrentThread());
   is_capturing_ = false;
   client_->OnError(from_here, reason);
 }
 
@@ skipping 16 matching lines @@
     DLOG(ERROR) << "Error mmap()ing a V4L2 buffer into userspace";
     return false;
   }
   start_ = static_cast<uint8_t*>(start);
   length_ = buffer.length;
   payload_size_ = 0;
   return true;
 }
 
 }  // namespace media