As mentioned in #229, the existing WebNN graph building (MLGraphBuilder.build) and execution (MLGraph.compute) are sync APIs. This is required by Wasm (C++) based ML framework's backend implementation. To avoid blocking the main thread, the good practice is to call these synchronous APIs in a worker context.

There are JavaScript based ML frameworks, like TensorFlow.js, that are mainly used in the main thread. Should WebNN support async APIs in the main thread? This would help not only the JS ML frameworks but also broader JS adoption of the API.

/cc @pyu10055