Revert "media/gpu shared memory: update v4l2 UnalignedSharedMemory"

This reverts commit cfe635ce.

Reason for revert: This breaks ARC++ (App and CTS/GTS). See detail in crbug.com/874074

Original change's description:
> media/gpu shared memory: update v4l2 UnalignedSharedMemory
> 
> Uses the new WritableUnalignedMapping class, which changes the ownership
> semantics. See the bug for details on the overall plan.
> 
> Bug: 849207
> Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
> Change-Id: Idacc45e249291bd9d42ff7bf9a8abffe8636f6cf
> Reviewed-on: https://chromium-review.googlesource.com/1117692
> Commit-Queue: Matthew Cary <mattcary@chromium.org>
> Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
> Reviewed-by: Alexandr Ilin <alexilin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#582270}

TBR=dcastagna@chromium.org,mattcary@chromium.org,alexilin@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 849207
Change-Id: I1fdf459f8b480da412854d0a86ece9a0ac86a1c8
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Reviewed-on: https://chromium-review.googlesource.com/1176841Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583487}

media/gpu/v4l2/v4l2_jpeg_decode_accelerator.cc

@@ -133,9 +133,8 @@ V4L2JpegDecodeAccelerator::JobRecord::JobRecord(
     const BitstreamBuffer& bitstream_buffer,
     scoped_refptr<VideoFrame> video_frame)
     : bitstream_buffer_id(bitstream_buffer.id()),
-      shm(bitstream_buffer.handle(),
-          bitstream_buffer.size(),
-          bitstream_buffer.offset()),
+      shm(bitstream_buffer.handle(), bitstream_buffer.size(), true),
+      offset(bitstream_buffer.offset()),
       out_frame(video_frame) {}
 
 V4L2JpegDecodeAccelerator::JobRecord::~JobRecord() {}
@@ -290,7 +289,7 @@ bool V4L2JpegDecodeAccelerator::IsSupported() {
 void V4L2JpegDecodeAccelerator::DecodeTask(
     std::unique_ptr<JobRecord> job_record) {
   DCHECK(decoder_task_runner_->BelongsToCurrentThread());
-  if (!job_record->shm.IsValid()) {
+  if (!job_record->shm.MapAt(job_record->offset, job_record->shm.size())) {
     VPLOGF(1) << "could not map bitstream_buffer";
     PostNotifyError(job_record->bitstream_buffer_id, UNREADABLE_INPUT);
     return;

media/gpu/v4l2/v4l2_jpeg_decode_accelerator.h

@@ -67,7 +67,9 @@ class MEDIA_GPU_EXPORT V4L2JpegDecodeAccelerator
     // Input image buffer ID.
     int32_t bitstream_buffer_id;
     // Memory mapped from |bitstream_buffer|.
-    WritableUnalignedMapping shm;
+    UnalignedSharedMemory shm;
+    // Offset used for shm.
+    off_t offset;
     // Output frame buffer.
     scoped_refptr<VideoFrame> out_frame;
   };

media/gpu/v4l2/v4l2_slice_video_decode_accelerator.cc

@@ -201,7 +201,8 @@ struct V4L2SliceVideoDecodeAccelerator::BitstreamBufferRef {
   ~BitstreamBufferRef();
   const base::WeakPtr<VideoDecodeAccelerator::Client> client;
   const scoped_refptr<base::SingleThreadTaskRunner> client_task_runner;
-  const std::unique_ptr<WritableUnalignedMapping> shm;
+  const std::unique_ptr<UnalignedSharedMemory> shm;
+  off_t offset;
   off_t bytes_used;
   const int32_t input_id;
 };
@@ -213,10 +214,11 @@ V4L2SliceVideoDecodeAccelerator::BitstreamBufferRef::BitstreamBufferRef(
     int32_t input_id)
     : client(client),
       client_task_runner(client_task_runner),
-      shm(buffer ? std::make_unique<WritableUnalignedMapping>(buffer->handle(),
-                                                              buffer->size(),
-                                                              buffer->offset())
+      shm(buffer ? std::make_unique<UnalignedSharedMemory>(buffer->handle(),
+                                                           buffer->size(),
+                                                           true)
                  : nullptr),
+      offset(buffer ? buffer->offset() : 0),
       bytes_used(0),
       input_id(input_id) {}
 
@@ -1347,12 +1349,12 @@ void V4L2SliceVideoDecodeAccelerator::DecodeTask(
       new BitstreamBufferRef(decode_client_, decode_task_runner_,
                              &bitstream_buffer, bitstream_buffer.id()));
 
-  // Skip empty buffer. This must be done after creating bitstream_record as the
-  // handle in the bitstream_buffer needs to be consumed.
+  // Skip empty buffer.
   if (bitstream_buffer.size() == 0)
     return;
 
-  if (!bitstream_record->shm->IsValid()) {
+  if (!bitstream_record->shm->MapAt(bitstream_record->offset,
+                                    bitstream_record->shm->size())) {
     VLOGF(1) << "Could not map bitstream_buffer";
     NOTIFY_ERROR(UNREADABLE_INPUT);
     return;

media/gpu/v4l2/v4l2_video_decode_accelerator.cc

@@ -78,7 +78,8 @@ struct V4L2VideoDecodeAccelerator::BitstreamBufferRef {
   ~BitstreamBufferRef();
   const base::WeakPtr<Client> client;
   const scoped_refptr<base::SingleThreadTaskRunner> client_task_runner;
-  const std::unique_ptr<WritableUnalignedMapping> shm;
+  const std::unique_ptr<UnalignedSharedMemory> shm;
+  off_t offset;
   size_t bytes_used;
   const int32_t input_id;
 };
@@ -97,10 +98,11 @@ V4L2VideoDecodeAccelerator::BitstreamBufferRef::BitstreamBufferRef(
     int32_t input_id)
     : client(client),
       client_task_runner(client_task_runner),
-      shm(buffer ? std::make_unique<WritableUnalignedMapping>(buffer->handle(),
-                                                              buffer->size(),
-                                                              buffer->offset())
+      shm(buffer ? std::make_unique<UnalignedSharedMemory>(buffer->handle(),
+                                                           buffer->size(),
+                                                           true)
                  : nullptr),
+      offset(buffer ? buffer->offset() : 0),
       bytes_used(0),
       input_id(input_id) {}
 
@@ -777,12 +779,12 @@ void V4L2VideoDecodeAccelerator::DecodeTask(
       new BitstreamBufferRef(decode_client_, decode_task_runner_,
                              &bitstream_buffer, bitstream_buffer.id()));
 
-  // Skip empty buffer. This must be done after creating bitstream_record as the
-  // handle in the bitstream_buffer needs to be consumed.
+  // Skip empty buffer.
   if (bitstream_buffer.size() == 0)
     return;
 
-  if (!bitstream_record->shm->IsValid()) {
+  if (!bitstream_record->shm->MapAt(bitstream_record->offset,
+                                    bitstream_record->shm->size())) {
     VLOGF(1) << "could not map bitstream_buffer";
     NOTIFY_ERROR(UNREADABLE_INPUT);
     return;

media/gpu/v4l2/v4l2_video_encode_accelerator.cc

@@ -89,10 +89,10 @@ static void CopyNALUPrependingStartCode(const uint8_t* src,
 namespace media {
 
 struct V4L2VideoEncodeAccelerator::BitstreamBufferRef {
-  BitstreamBufferRef(int32_t id, std::unique_ptr<WritableUnalignedMapping> shm)
+  BitstreamBufferRef(int32_t id, std::unique_ptr<UnalignedSharedMemory> shm)
       : id(id), shm(std::move(shm)) {}
   const int32_t id;
-  const std::unique_ptr<WritableUnalignedMapping> shm;
+  const std::unique_ptr<UnalignedSharedMemory> shm;
 };
 
 V4L2VideoEncodeAccelerator::InputRecord::InputRecord() : at_device(false) {}
@@ -309,9 +309,9 @@ void V4L2VideoEncodeAccelerator::UseOutputBitstreamBuffer(
     return;
   }
 
-  auto shm = std::make_unique<WritableUnalignedMapping>(
-      buffer.handle(), buffer.size(), buffer.offset());
-  if (!shm->IsValid()) {
+  auto shm = std::make_unique<UnalignedSharedMemory>(buffer.handle(),
+                                                     buffer.size(), false);
+  if (!shm->MapAt(buffer.offset(), buffer.size())) {
     NOTIFY_ERROR(kPlatformFailureError);
     return;
   }