Add abort reason to AbortSignal

dom.bs

@@ -1743,7 +1743,7 @@ interface AbortController {
 
  <dt><code><var>controller</var> . <a method for=AbortController lt=abort()>abort</a>(reason)</code>
  <dd>Invoking this method will set this object's {{AbortSignal}}'s [=AbortSignal/aborted flag=],
- store the <var ignore>reason</var> in this object's {{AbortSignal}}'s [=AbortSignal/abort reason=], and
+ store <var ignore>reason</var> in this object's {{AbortSignal}}'s [=AbortSignal/abort reason=], and
  signal to any observers that the associated activity is to be aborted.
 </dl>
 
@@ -1784,12 +1784,12 @@ interface AbortSignal : EventTarget {
 <dl class=domintro>
  <dt><code>AbortSignal . <a method for=AbortSignal>abort</a>(reason)</code>
  <dd>Returns an {{AbortSignal}} instance whose <a for=AbortSignal>aborted flag</a> is set, and
- <a for=AbortSignal>abort reason</a> is set to <var>reason</var> if provided, otherwise to
+ <a for=AbortSignal>abort reason</a> is set to <var>reason</var> if provided, otherwise to an
  "{{AbortError!!exception}}" {{DOMException}}.
 
  <dt><code><var>signal</var> . <a attribute for=AbortSignal>reason</a></code>
- <dd>Returns the <a for=AbortSignal>abort reason</a> for an {{AbortSignal}} if it has been
- set; by default this will be an "{{AbortError!!exception}}" {{DOMException}}.
+ <dd>Returns the <a for=AbortSignal>abort reason</a> for an {{AbortSignal}}; by default this will
+ be an "{{AbortError!!exception}}" {{DOMException}}.
 
  <dt><code><var>signal</var> . <a attribute for=AbortSignal>aborted</a></code>
  <dd>Returns true if this {{AbortSignal}}'s {{AbortController}} has signaled to abort; otherwise
@@ -1856,7 +1856,7 @@ service worker.
 them. For instance, if the operation has already completed.
 
 <p>To <dfn export for=AbortSignal>signal abort</dfn>, given an {{AbortSignal}} object
-<var>signal</var> and an optional abort <var>reason</var>, run these steps:
+<var>signal</var> and an optional <var>reason</var>, run these steps:
 
 <ol>
  <li><p>If <var>signal</var>'s [=AbortSignal/aborted flag=] is set, then return.