Add navigator.hardwareConcurrency

Fixes #879. Originally found in https://wiki.whatwg.org/wiki/NavigatorCores.

source

@@ -88733,16 +88733,17 @@ scheduleWork(); // queues a task to do lots of work</pre>
 <span>Navigator</span> implements <span>NavigatorOnLine</span>;
 <span>Navigator</span> implements <span>NavigatorContentUtils</span>;
 <span>Navigator</span> implements <span>NavigatorCookies</span>;
-<span>Navigator</span> implements <span>NavigatorPlugins</span>;</pre>
+<span>Navigator</span> implements <span>NavigatorPlugins</span>;
+<span>Navigator</span> implements <span>NavigatorConcurrentHardware</span>;</pre>
 
 <!-- v2:
   geolocator mozIsLocallyAvailable preference
 -->
 
   <div w-nodev>
 
-  <p>These interfaces are defined separately so that other specifications can re-use parts of the
-  <code>Navigator</code> interface.</p>
+  <p>These interfaces are defined separately so that <code>WorkerNavigator</code> can re-use parts
+  of the <code>Navigator</code> interface.</p>
 
   </div>
 
@@ -95226,6 +95227,33 @@ interface <dfn>SharedWorker</dfn> : <span>EventTarget</span> {
 
   </ol>
 
+  <h4 id="navigator.hardwareconcurrency">Concurrent hardware capabilities</h4>
+
+  <pre class="idl">[NoInterfaceObject, Exposed=(Window,Worker)]
+interface <dfn>NavigatorConcurrentHardware</dfn> {
+  readonly attribute unsigned long long <span data-x="dom-navigator-hardwareConcurrency">hardwareConcurrency</span>;
+};</pre>
+
+  <dl class="domintro">
+   <dt><var>window</var> . <code data-x="dom-navigator">navigator</code> . <code subdfn data-x="dom-navigator-hardwareConcurrency">hardwareConcurrency</code></dt>
+
+   <dd>Returns the number of logical processors potentially available to the user agent.</dd>
+  </dl>
+
+  <div w-nodev>
+
+  <p>The <dfn><code
+  data-x="dom-navigator-hardwareConcurrency">navigator.hardwareConcurrency</code></dfn> attribute's
+  getter must return a number between 1 and the number of logical processors potentially available
+  to the user agent. If this cannot be determined, the getter must return 1.
+  <!--INSERT FINGERPRINT--></p>
+
+  <p>User agents should err toward exposing the number of logical processors available, using lower
+  values only in cases where there are user-agent specific limits in place (such as a limitation
+  on the number of <span data-x="Worker">workers</span> that can be created) or when the user agent
+  desires to limit fingerprinting possibilities.</p>
+
+  </div>
 
   <h3>APIs available to workers</h3>
 
@@ -95360,7 +95388,8 @@ interface <dfn>SharedWorker</dfn> : <span>EventTarget</span> {
 interface <dfn>WorkerNavigator</dfn> {};
 <span>WorkerNavigator</span> implements <span>NavigatorID</span>;
 <span>WorkerNavigator</span> implements <span>NavigatorLanguage</span>;
-<span>WorkerNavigator</span> implements <span>NavigatorOnLine</span>;</pre>
+<span>WorkerNavigator</span> implements <span>NavigatorOnLine</span>;
+<span>WorkerNavigator</span> implements <span>NavigatorConcurrentHardware</span>;</pre>
 
 
 
@@ -117301,6 +117330,7 @@ INSERT INTERFACES HERE
   Ehsan Akhgari,
   Eira Monstad,
   Eitan Adler,
+  Eli Grey,
   Eliot Graff,
   Elisabeth Robson,
   Elizabeth Castro,