Conditionally expose legacy touch event APIs (#111)

Fixes #64

index.html

@@ -949,9 +949,16 @@ <h2>Retargeting</h2>
       </ol>
     </section>
 
+    <section>
+      <h2>Conditionally exposing legacy touch event APIs</h2>
+      <p>User agents have an associated boolean <dfn>expose legacy touch event APIs</dfn> whose value is <a>implementation-defined</a>.</p>
+
+      <p class="note">Existing web content often use the existance of these APIs as a signal that the user agent is a touch-enabled "mobile" device, and therefore exposing these APIs on non-mobile devices, even if they are touch-enabled, could lead to a suboptimal user experience for such web content.</p>
+    </section>
+
     <section>
       <h2>Extensions to the <code>GlobalEventHandlers</code> mixin</h2>
-      <p>The following section describes extensions to the existing <dfn data-cite="HTML5#globaleventhandlers">GlobalEventHandlers</dfn> mixin, defined in [[!HTML5]], to facilitate the event handler registration.</p>
+      <p>The following section describes extensions to the existing <dfn data-cite="HTML5#globaleventhandlers">GlobalEventHandlers</dfn> mixin, defined in [[!HTML5]], to facilitate the event handler registration. For user agents where <a>expose legacy touch event APIs</a> is false, this mixin must not be implemented.</p>
       <pre class="idl">
 partial interface mixin GlobalEventHandlers {
                     attribute EventHandler ontouchstart;