Bug 2045769 - Check required snapshot shmem size against actual size. a=RyanVM

  gfx::SurfaceFormat ssFormat = aSurface->GetFormat();

  auto stride = ImageDataSerializer::ComputeRGBStride(ssFormat, ssSize.width);

  size_t sizeRequired =

      ImageDataSerializer::ComputeRGBBufferSize(ssSize, ssFormat);

  if (!sizeRequired) {

    return nullptr;

  }

  sizeRequired = ipc::shared_memory::PageAlignedSize(sizeRequired);

  // Shmem is only valid if the surface is the latest snapshot (not detached).

  if (!aDetached) {

    // If there is a shmem associated with this snapshot id, then we want to try

    // use that directly without having to allocate a new shmem for retrieval.

    // to use that directly instead of allocating a new shmem for retrieval.

    // Also check that it meets the size required.

    auto it = mTextureInfo.find(aTextureOwnerId);

    if (it != mTextureInfo.end() && it->second.mSnapshotShmem) {

    if (it != mTextureInfo.end() && it->second.mSnapshotShmem &&

        !NS_WARN_IF(sizeRequired > it->second.mSnapshotShmem->Size())) {

      const auto* shmemPtr = it->second.mSnapshotShmem->DataAs<uint8_t>();

      MOZ_ASSERT(shmemPtr);

      mRecorder->RecordEvent(RecordedPrepareShmem(aTextureOwnerId));