Introduce DOMQuad.fromQuad(). Fixes https://www.w3.org/Bugs/Public/show_bug.cgi?id=27492

Author: zcorpan

geometry/Overview.bs

@@ -281,13 +281,21 @@ Objects implementing the <a interface>DOMQuad</a> interface represents a <dfn>qu
  Exposed=(Window,Worker)]
 interface DOMQuad {
     [NewObject] static DOMQuad fromRect(optional DOMRectInit other);
+    [NewObject] static DOMQuad fromQuad(optional DOMQuadInit other);
 
     [SameObject] readonly attribute DOMPoint p1;
     [SameObject] readonly attribute DOMPoint p2;
     [SameObject] readonly attribute DOMPoint p3;
     [SameObject] readonly attribute DOMPoint p4;
     [SameObject] readonly attribute DOMRectReadOnly bounds;
 };
+
+dictionary DOMQuadInit {
+  DOMPointInit p1;
+  DOMPointInit p2;
+  DOMPointInit p3;
+  DOMPointInit p4;
+};
 </pre>
 
 The <dfn dfn-type=constructor dfn-for=DOMQuad><code>DOMQuad(<var>p1</var>, <var>p2</var>, <var>p3</var>, <var>p4</var>)</code></dfn> constructor, when invoked, must run the following steps:
@@ -313,6 +321,18 @@ The <dfn dfn-for=DOMQuad><code>fromRect(<var>other</var>)</code></dfn> static me
   <li><p>Return a new <a interface>DOMQuad</a> with <a attribute for=DOMQuad>p1</a> set to <var>point 1</var>, <a attribute for=DOMQuad>p2</a> set to <var>point 2</var>, <a attribute for=DOMQuad>p3</a> set to <var>point 3</var> and <a attribute for=DOMQuad>p4</a> set to <var>point 4</var>, and let the <a>associated bounding rectangle</a> be <var>bounds</var>.
 </ol>
 
+The <dfn dfn-for=DOMQuad><code>fromQuad(<var>other</var>)></code></dfn> static method on {{DOMQuad}} must run the following steps:
+
+1. Let <var>point 1</var> be the result of invoking {{DOMPoint/fromPoint()}} static method on {{DOMPoint}} with the {{DOMQuadInit/p1}} dictionary member of <var>other</var> as argument, if it exists.
+1. Let <var>point 2</var> be the result of invoking {{DOMPoint/fromPoint()}} static method on {{DOMPoint}} with the {{DOMQuadInit/p2}} dictionary member of <var>other</var> as argument, if it exists.
+1. Let <var>point 3</var> be the result of invoking {{DOMPoint/fromPoint()}} static method on {{DOMPoint}} with the {{DOMQuadInit/p3}} dictionary member of <var>other</var> as argument, if it exists.
+1. Let <var>point 4</var> be the result of invoking {{DOMPoint/fromPoint()}} static method on {{DOMPoint}} with the {{DOMQuadInit/p4}} dictionary member of <var>other</var> as argument, if it exists.
+1. Return a new {{DOMQuad}} with
+    {{DOMQuad/p1}} set to <var>point 1</var>,
+    {{DOMQuad/p2}} set to <var>point 2</var>,
+    {{DOMQuad/p3}} set to <var>point 3</var> and
+    {{DOMQuad/p4}} set to <var>point 4</var>.
+
 <div dfn-type=attribute dfn-for=DOMQuad>
  The <dfn>p1</dfn> attribute must return a <a interface>DOMPoint</a> that represents <a attribute>p1</a> of the quadrilateral it was invoked on. The author can modify the returned <a interface>DOMPoint</a> object, which directly affects the quadrilateral.