Clarify that webglcontextcreationerror must be fired synchronously to JS.

If webgl context creation fails, canvas.getContext will return null and fire webglcontextcreationerror to the canvas. From the spec wording in https://www.khronos.org/registry/webgl/specs/latest/1.0/#2.1, it is not immediately clear if this event is fired synchronously or asynchronously (e.g. at a later turn of the browser event loop).

Looking at the example code in https://www.khronos.org/registry/webgl/specs/latest/1.0/#fire-a-webgl-context-creation-error however, it illustrates that the intent is that the error is always raised synchronously, since the code prints out the error immediately after calling getContext.

I propose that step 6.1 in https://www.khronos.org/registry/webgl/specs/latest/1.0/#2.1 is updated to explicitly state that the event will be synchronously delivered.

Read section 2.1 and the “fire a webglcontextcreationerror” example linked in the issue, focusing on step 6.1 and the timing implied by the example. Update the specification wording to explicitly say the event is delivered synchronously, and confirm that the wording matches the example’s behavior.