Editorial: specify behavior for omitted opt params

Explicitly specify the value that should be used when optional
parameters are not provided. Update some function signatures to
highlight the modifications included in this proposal. Additionally,
update the signature of the SharedArrayBuffer constructor to reflect a
recent change in ECMA262 [1].

[1] tc39/ecma262#2393

spec.html

@@ -130,11 +130,12 @@ <h1>HostResizeArrayBuffer ( _buffer_, _newByteLength_ )</h1>
     <h1>The ArrayBuffer Constructor</h1>
 
     <emu-clause id="sec-arraybuffer-length">
-      <h1>ArrayBuffer ( _length_ [ , _options_ ] )</h1>
+      <h1>ArrayBuffer ( _length_<ins>[ , _options_ ]</ins> )</h1>
       <p>When the `ArrayBuffer` function is called with argument _length_<ins> and optional argument _options_</ins>, the following steps are taken:</p>
       <emu-alg>
         1. If NewTarget is *undefined*, throw a *TypeError* exception.
         1. Let _byteLength_ be ? ToIndex(_length_).
+        1. <ins>If _options_ is not present, set _options_ to *undefined*.</ins>
         1. <ins>Let _requestedMaxByteLength_ be ? GetArrayBufferMaxByteLengthOption(_options_).</ins>
         1. <ins>If _requestedMaxByteLength_ is ~empty~, then</ins>
           1. <ins>Return ? AllocateArrayBuffer(NewTarget, _byteLength_).</ins>
@@ -218,7 +219,7 @@ <h1>ArrayBuffer.prototype.transfer ( [ _newLength_ ] )</h1>
         1. Perform ? RequireInternalSlot(_O_, [[ArrayBufferData]]).
         1. If IsSharedArrayBuffer(_O_) is *true*, throw a *TypeError* exception.
         1. If IsDetachedBuffer(_O_) is *true*, throw a *TypeError* exception.
-        1. If _newLength_ is *undefined*, let _newByteLength_ be _O_.[[ArrayBufferByteLength]].
+        1. If _newLength_ is not present or if _newLength_ is *undefined*, let _newByteLength_ be _O_.[[ArrayBufferByteLength]].
         1. Else, let _newByteLength_ be ? ToIntegerOrInfinity(_newLength_).
         1. Let _new_ be ? Construct(%ArrayBuffer%, &laquo; 𝔽(_newByteLength_) &raquo;).
         1. NOTE: This method returns a fixed-length ArrayBuffer.
@@ -295,11 +296,12 @@ <h1>HostGrowSharedArrayBuffer ( _buffer_, _newByteLength_ )</h1>
     <h1>The SharedArrayBuffer Constructor</h1>
 
     <emu-clause id="sec-sharedarraybuffer-length">
-      <h1>SharedArrayBuffer ( [ _length_ [ , _options_ ] ] )</h1>
-      <p>When the `SharedArrayBuffer` function is called with optional arguments _length_ and _options_, the following steps are taken:</p>
+      <h1>SharedArrayBuffer ( _length_<ins>[ , _options_ ]</ins> )</h1>
+      <p>When the `SharedArrayBuffer` function is called with argument _length_<ins> and optional argument _options_</ins>, the following steps are taken:</p>
       <emu-alg>
         1. If NewTarget is *undefined*, throw a *TypeError* exception.
         1. Let _byteLength_ be ? ToIndex(_length_).
+        1. <ins>If _options_ is not present, set _options_ to *undefined*.</ins>
         1. <ins>Let _requestedMaxByteLength_ be ? GetArrayBufferMaxByteLengthOption(_options_).</ins>
         1. <ins>If _requestedMaxByteLength_ is ~empty~, then</ins>
           1. <ins>Return ? AllocateSharedArrayBuffer(NewTarget, _byteLength_).</ins>