Allow notifications and actions to specify a navigable URL

This makes notifications more declarative by not requiring explicit handling of the clicks by the web application.

notifications.bs

@@ -60,6 +60,9 @@ or "<code>rtl</code>").
 <p>A <a for=/>notification</a> has an associated <dfn for=notification id=body>body</dfn> (a
 string).
 
+<p>A <a for=/>notification</a> has an associated <dfn for=notification>URL</dfn> (null or a
+<a for=/>URL</a>). It is initially null.
+
 <p>A <a for=/>notification</a> has an associated <dfn for=notification id=tag>tag</dfn> (a string).
 
 <p>A <a for=/>notification</a> has an associated <dfn for=notification id=data>data</dfn> (a
@@ -136,6 +139,9 @@ for an end user. Each <a for=/>action</a> has an associated:
  <dt><dfn for=action id=action-title>title</dfn>
  <dd>A string.
 
+ <dt><dfn for=action>URL</dfn>
+ <dd>Null or a <a for=/>URL</a>. It is initially null.
+
  <dt><dfn for=action>icon URL</dfn>
  <dd>Null or a <a for=/>URL</a>. It is initially null.
 
@@ -219,6 +225,11 @@ clipped corners.
  <li><p>Set <var>notification</var>'s <a for=notification>body</a> to
  <var>options</var>["{{NotificationOptions/body}}"].
 
+ <li><p>If <var>options</var>["{{NotificationOptions/url}}"] <a for=map>exists</a>, then
+ <a lt="URL parser">parse</a> it using <var>baseURL</var>, and if that does not return failure, set
+ <var>notification</var>'s <a for=notification>URL</a> to the return value. (Otherwise
+ <var>notification</var>'s <a for=notification>URL</a> remains null.)
+
  <li><p>Set <var>notification</var>'s <a for=notification>tag</a> to
  <var>options</var>["{{NotificationOptions/tag}}"].
 
@@ -269,6 +280,11 @@ clipped corners.
    <li><p>Set <var>action</var>'s <a for=action>title</a> to
    <var>entry</var>["{{NotificationAction/title}}"].
 
+   <li><p>If <var>entry</var>["{{NotificationAction/url}}"] <a for=map>exists</a>, then
+   <a lt="URL parser">parse</a> it using <var>baseURL</var>, and if that does not return failure,
+   set <var>action</var>'s <a for=action>URL</a> to the return value. (Otherwise <var>action</var>'s
+   <a for=action>URL</a> remains null.)
+
    <li><p>If <var>entry</var>["{{NotificationAction/icon}}"] <a for=map>exists</a>, then
    <a lt="URL parser">parse</a> it using <var>baseURL</var>, and if that does not return failure,
    set <var>action</var>'s <a for=action>icon URL</a> to the return value. (Otherwise
@@ -536,14 +552,39 @@ interpreted as a language tag. Validity or well-formedness are not enforced. [[!
 platform supports activation, the user agent must (unless otherwise specified) run these steps:
 
 <ol>
+ <li><p>Let <var>action</var> be null.
+
+ <li><p>If one of <var>notification</var>'s <a for=notification>actions</a> was activated by the end
+ user, then set <var>action</var> to that <a for=/>action</a>.
+
+ <li><p>Let <var>url</var> be <var>notification</var>'s <a for=notification>URL</a>.
+
+ <li>
+  <p>If <var>action</var> is non-null, then set <var>url</var> to <var>action</var>'s
+  <a for=action>URL</a>.
+
+  <p class=note>This intentionally makes it so that when an <a for=/>action</a>'s
+  <a for=action>URL</a> is null, it falls through to the <code>click</code> event, providing more
+  flexibility to the web developer.
+
+ <li>
+  <p>If <var>url</var> is non-null:
+
+  <ol>
+   <li><p><a>Create a fresh top-level traversable</a> given <var>url</var>.
+   <!-- Should maybe set userInvolvement correctly here, even though it doesn't do anything today. -->
+
+   <li><p>Return.
+  </ol>
+
  <li>
   <p>If <var>notification</var> is a <a>persistent notification</a>, then:
 
   <ol>
-   <li><p>Let <var>action</var> be the empty string.
+   <li><p>Let <var>actionName</var> be the empty string.
 
-   <li><p>If one of <var>notification</var>'s <a for=notification>actions</a> was activated by the
-   user, then set <var>action</var> to that <a for=/>action</a>'s <a for=action>name</a>.
+   <li><p>If <var>action</var> is non-null, then set <var>actionName</var> to <var>action</var>'s
+   <a for=action>name</a>.
 
    <li><a>Fire a service worker notification event</a> named "<code>notificationclick</code>" given
    <var>notification</var> and <var>action</var>.
@@ -637,6 +678,7 @@ interface Notification : EventTarget {
   readonly attribute NotificationDirection dir;
   readonly attribute DOMString lang;
   readonly attribute DOMString body;
+  readonly attribute USVString url;
   readonly attribute DOMString tag;
   readonly attribute USVString image;
   readonly attribute USVString icon;
@@ -656,6 +698,7 @@ dictionary NotificationOptions {
   NotificationDirection dir = "auto";
   DOMString lang = "";
   DOMString body = "";
+  USVString url;
   DOMString tag = "";
   USVString image;
   USVString icon;
@@ -684,6 +727,7 @@ enum NotificationDirection {
 dictionary NotificationAction {
   required DOMString action;
   required DOMString title;
+  USVString url;
   USVString icon;
 };
 
@@ -849,6 +893,16 @@ return the <a>maximum number of actions</a> supported.
 <p>The <dfn attribute for=Notification><code>body</code></dfn> getter steps are to return
 <a>this</a>'s <a for=/>notification</a>'s <a for=notification>body</a>.
 
+<p>The <dfn attribute for=Notification><code>url</code></dfn> getter steps are:
+
+<ol>
+ <li><p>If <a>this</a>'s <a>notification</a>'s <a for=notification>URL</a> is null, then return the
+ empty string.
+
+ <li><p>Return <a>this</a>'s <a>notification</a>'s <a for=notification>URL</a>,
+ <a lt="URL serializer">serialized</a>.
+</ol>
+
 <p>The <dfn attribute for=Notification><code>tag</code></dfn> getter steps are to return
 <a>this</a>'s <a for=/>notification</a>'s <a for=notification>tag</a>.
 
@@ -921,6 +975,10 @@ then return null.
    <li><p>Set <var>action</var>["{{NotificationAction/title}}"] to <var>entry</var>'s
    <a for=action>title</a>.
 
+   <li><p>If <var>entry</var>'s <a for=action>URL</a> is non-null, then set
+   <var>action</var>["{{NotificationAction/url}}"] to <var>entry</var>'s <a for=action>URL</a>,
+   <a lt="URL serializer">serialized</a>.
+
    <li><p>If <var>entry</var>'s <a for=action>icon URL</a> is non-null, then set
    <var>action</var>["{{NotificationAction/icon}}"] to <var>entry</var>'s
    <a for=action>icon URL</a>, <a lt="URL serializer">serialized</a>.