Remove unnecessary step from [[doClose]]

When [[onClose]]() throws, we just call [[error]] and it rejects [[closedPromise]].
Use more distinguishable name for BWS.[[doAbort]] arg

"r" is bound to the reason with which abortResult is rejected later in the step 6. Let's use some other name for the argument of [[doAbort]] function not to confuse readers.
Merge remote-tracking branch 'upstream/master' into patch-6
Set [[pulling]] in [[callPull]] also in the reference impl

Apply the change 9ce45f in the spec to the reference implementation