[ServiceWorker] Confusing use of `transforming with` and `Upon fulfillment`. (#621)

Several algorithms contain steps like the following two:

1. Let p be [transforming responseArrayPromise with onFulfilled](http://www.w3.org/2001/tag/doc/promises-guide#transforming-by).
1. [Upon fulfillment of p with value](http://www.w3.org/2001/tag/doc/promises-guide#upon-fulfillment) responseArray, perform the following substeps, onFulfilled, in parallel:

`onFulfilled` isn't defined except in the _Upon fulfillment_ substeps, but it's odd to see it used twice. In some cases, like [add()](https://slightlyoff.github.io/ServiceWorker/spec/service_worker/#cache-add-method), the second use is inconsistent because it tries to resolve the already-fulfilled promise. Some other cases, like [addAll()](https://slightlyoff.github.io/ServiceWorker/spec/service_worker/#cache-addAll-method), define `onFulfilled` twice, in different ways.

I suspect you don't mean to use "Upon fulfillment" after "transforming" at all.

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Reply to this email directly or view it on GitHub:
https://github.com/slightlyoff/ServiceWorker/issues/621