Buffer Map Extended Usages

Overview:

• The wgpu::Feature::BufferMapExtendedUsages feature allows creating a buffer with wgpu::BufferUsage::MapRead and/or wgpu::BufferUsage::MapWrite and any other wgpu::BufferUsage.

Example Usage:

wgpu::BufferDescriptor descriptor;
descriptor.size = size;
descriptor.usage = wgpu::BufferUsage::MapWrite | wgpu::BufferUsage::Uniform;
wgpu::Buffer uniformBuffer = device.CreateBuffer(&descriptor);

uniformBuffer.MapAsync(wgpu::MapMode::Write, 0, size,
   [](WGPUBufferMapAsyncStatus status, void* userdata)
   {
      wgpu::Buffer* buffer = static_cast<wgpu::Buffer*>(userdata);
      memcpy(buffer->GetMappedRange(), data, sizeof(data));
   },
   &uniformBuffer);