WebGL's DrawingBuffer has a involved dance to create a GpuMemoryBuffer,
ImageCHROMIUM and associated texture. Instead, as sunnyps@ suggests in
[2], we could try and use TexStorage2DImageCHROMIUM() to let most of 
the operations happen on (gpu/viz) service side.

[1] https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/graphics/gpu/drawing_buffer.cc?q=DrawingBuffer::CreateColorBuffer+gpu_memory_buffer&sq=package:chromium&dr=CSs&l=1410
[2] https://chromium-review.googlesource.com/c/chromium/src/+/1404705/3/third_party/blink/renderer/platform/graphics/canvas_resource.cc#765