Rewrite processing shortcuts algorithm to be more precise (#832)

Normative changes:

* shortcuts that meet certain failure conditions are ignored.
  * Checks that name and url are present, URL is valid and within scope of the manifest.

Other changes:

* Clarify that the ShortcutItem url member needs to be within scope.
* Rewrite processing shortcuts algorithm as an ordered list.
* Creates a new array and returns it, rather than discarding the result.
* Explicitly says where developer warnings should be issued.

Closes #831

index.html

@@ -1531,7 +1531,7 @@ <h3>
           </li>
           <li>Set <var>manifest</var>["<a>shortcuts</a>"] to the result of
           running <a>processing the <code>shortcuts</code> member</a> given
-          <var>manifest URL</var>, and <code>"shortcuts"</code>.
+          <var>manifest</var>["<a>shortcuts</a>"] and <var>manifest URL</var>.
           </li>
           <li>
             <a>Extension point</a>: process any proprietary and/or other
@@ -2345,17 +2345,43 @@ <h3>
           are given by the following algorithm. The algorithm takes a
           <a data-cite=
           "WEBIDL#sequence-type">sequence</a>&lt;<a>ShortcutItem</a>&gt;
-          <var>shortcuts</var> as an argument. This algorithm returns an
-          <a data-cite=
-          "WEBIDL#sequence-type">sequence</a>&lt;<a>ShortcutItem</a>&gt;. For
-          each <var>shortcut</var> (<a>ShortcutItem</a>) in the sequence, set
-          <var>shortcut.icons</var> to the result of running <a>processing
-          `ImageResource` members</a> given <var>shortcut.icons</var> and
-          <var>manifest URL</var>. For each <var>shortcut</var>
-          (<a>ShortcutItem</a>) in the sequence, parse
-          <var>shortcut</var>["<a>url</a>"] using <var>manifest URL</var> as
-          the base URL.
+          <var>shortcuts</var> and a <a>URL</a> <var>manifest URL</var>. This
+          algorithm returns a <a data-cite=
+          "WEBIDL#sequence-type">sequence</a>&lt;<a>ShortcutItem</a>&gt;.
         </p>
+        <ol>
+          <li>Let <var>processedShortcuts</var> be a new Array object created
+          as if by the expression [].
+          </li>
+          <li>For each <var>shortcut</var> (<a>ShortcutItem</a>) in the
+          sequence:
+            <ol>
+              <li>If <var>shortcut</var>["name"] or <var>shortcut</var>["url"]
+              are undefined, or if <var>shortcut</var>["name"] is the empty
+              string, <a>issue a developer warning</a> and <a>continue</a>.
+              </li>
+              <li>Set <var>shortcut</var>["icons"] to the result of running <a>
+                processing `ImageResource` members</a> given
+                <var>shortcut</var>["icons"] and <var>manifest URL</var>.
+              </li>
+              <li>Set <var>shortcut</var>["url"] to the result of
+              <a>parsing</a> <var>shortcut</var>["url"] using <var>manifest
+              URL</var> as the base URL. If the result is failure, <a>issue a
+              developer warning</a> and <a>continue</a>.
+              </li>
+              <li>If <var>shortcut</var>["url"] is not <a>within scope</a> of
+              <var>manifest URL</var>, <a>issue a developer warning</a> and <a>
+                continue</a>.
+              </li>
+              <li>
+                <a>Append</a> <var>shortcut</var> to
+                <var>processedShortcuts</var>.
+              </li>
+            </ol>
+          </li>
+          <li>Return <var>processedShortcuts</var>.
+          </li>
+        </ol>
         <p>
           A user agent SHOULD expose shortcuts via interactions that are
           consistent with exposure of an application icon's context menu in the
@@ -3022,7 +3048,8 @@ <h3>
         </h3>
         <p>
           The <dfn>url</dfn> member of a <a>ShortcutItem</a> is the <a>URL</a>
-          that opens when the associated shortcut is activated.
+          <a data-lt="within scope of a manifest">within the application's
+          scope</a> that opens when the associated shortcut is activated.
         </p>
       </section>
       <section data-dfn-for="ShortcutItem" data-link-for="ShortcutItem">
@@ -3886,6 +3913,9 @@ <h3>
             <li>
               <dfn data-cite="INFRA#list-contain">contains</dfn>
             </li>
+            <li>
+              <dfn data-cite="INFRA#iteration-continue">continue</dfn>
+            </li>
           </ul>
         </li>
         <li>[[ECMASCRIPT]] defines the following terms: