media/gpu/v4l2: add sequence checker to V4L2Device

The V4L2Device class has grown a bit chaotically, and proper sequence
checking is not currently being enforced, although other classes of the
same unit (V4L2Queue notably) do sequence checking.

Add a sequence checker for the queue-related methods, which must always
be called from the client's sequence. The use of this checker will be
expanded to new use-cases and hopefully to older ones as well as we
confirm they are safe.

Bug: 1003223
Test: vdatests passing on Kevin.
Change-Id: I60aa8eb52e48a13fa99c42990af2f621982c44e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1799651
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Auto-Submit: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#696044}

media/gpu/v4l2/v4l2_device.cc

@@ -1005,11 +1005,15 @@ class V4L2QueueFactory {
   }
 };
 
-V4L2Device::V4L2Device() {}
+V4L2Device::V4L2Device() {
+  DETACH_FROM_SEQUENCE(client_sequence_checker_);
+}
 
 V4L2Device::~V4L2Device() {}
 
 scoped_refptr<V4L2Queue> V4L2Device::GetQueue(enum v4l2_buf_type type) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(client_sequence_checker_);
+
   switch (type) {
     // Supported queue types.
     case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
@@ -1034,6 +1038,8 @@ scoped_refptr<V4L2Queue> V4L2Device::GetQueue(enum v4l2_buf_type type) {
 }
 
 void V4L2Device::OnQueueDestroyed(v4l2_buf_type buf_type) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(client_sequence_checker_);
+
   auto it = queues_.find(buf_type);
   DCHECK(it != queues_.end());
   queues_.erase(it);

media/gpu/v4l2/v4l2_device.h

@@ -20,6 +20,7 @@
 #include "base/files/scoped_file.h"
 #include "base/memory/ref_counted.h"
 #include "base/optional.h"
+#include "base/sequence_checker.h"
 #include "media/base/video_decoder_config.h"
 #include "media/base/video_frame.h"
 #include "media/base/video_frame_layout.h"
@@ -548,6 +549,8 @@ class MEDIA_GPU_EXPORT V4L2Device
   // Callback that is called upon a queue's destruction, to cleanup its pointer
   // in queues_.
   void OnQueueDestroyed(v4l2_buf_type buf_type);
+
+  SEQUENCE_CHECKER(client_sequence_checker_);
 };
 
 }  //  namespace media