Brought back icon density member (closes #118)

index.html

@@ -167,8 +167,10 @@ <h2>
         [[\GetOwnProperty]]</a></dfn> operation and the abstract operation
         <dfn><a href=
         "http://people.mozilla.org/~jorendorff/es6-draft.html#sec-hasownproperty">
-        hasOwnProperty</a></dfn>, and the <a class="external" href=
-        "http://people.mozilla.org/~jorendorff/es6-draft.html#sec-ecmascript-data-types-and-values">
+        hasOwnProperty</a></dfn>, <dfn title="parseFloat"><a href=
+        "http://people.mozilla.org/~jorendorff/es6-draft.html#sec-parsefloat-string">
+        parseFloat(string)</a></dfn> function, and the <a class="external"
+        href="http://people.mozilla.org/~jorendorff/es6-draft.html#sec-ecmascript-data-types-and-values">
         <dfn>Type</dfn>(<var>x</var>)</a> notation are defined in
         [[!ECMASCRIPT]].
       </p>
@@ -1200,6 +1202,39 @@ <h3>
 </pre>
         </div>
       </section>
+      <section>
+        <h3>
+          <code>density</code> member
+        </h3>
+        <p>
+          The <dfn id="icon-densitiy">density</dfn> member of an icon is the
+          device pixel density for which this icon was designed. The device
+          pixel density is expressed as the number of dots per 'px' unit
+          (equivalent to a dppx as defined in [[!css3-values]]). The value is a
+          positive number greater than 0. If the developer ommits the value,
+          the user agent assumes the value <code>1.0</code>.
+        </p>
+        <p>
+          The <dfn id="dfn-steps-for-processing-a-density-of-an-icon">steps for
+          processing a density of an icon</dfn> are given by the following
+          algorithm. The algorithm thanks an <var>icon</var> object as an
+          argument and returns a positive number.
+        </p>
+        <ol>
+          <li>Let <var>value</var> be the result of calling the
+          [[\GetOwnProperty]] internal method of <var>icon</var> passing
+          "<code>density</code>" as the argument.
+          </li>
+          <li>Let <var>result</var> be the result of
+          <a>parseFloat</a>(<var>value</var>);
+          </li>
+          <li>If <var>result</var> is <code>NaN</code>, +0, −0, +∞, or −∞, or
+          less than 0, let <var>result</var> be 1.0.
+          </li>
+          <li>Return <var>result</var>.
+          </li>
+        </ol>
+      </section>
       <section>
         <h3>
           <code>sizes</code> member