surface failed fetches in the performance timeline

- fetches that are blocked (CSP, CORS, etc) are omitted
- fetches aborted due to network/other errors must be included
- failed fetches must surface initialized attributes up to point of
  failure

Closes #12.

index.html

@@ -257,12 +257,9 @@ <h3>Introduction</h3>
 
 <section id="resources-included">
 <h3>Resources Included in the <code><a href="#performanceresourcetiming">PerformanceResourceTiming</a></code> Interface</h3>
-<p>
-	All resources <a title='fetch' href="http://www.w3.org/TR/html5/infrastructure.html#fetch">fetched</a> by the current <a href="http://www.w3.org/TR/html5/browsers.html#browsing-context">browsing</a> [[!HTML5]] or worker [[!WORKERS]] context's MUST be included as <a href="#performanceresourcetiming">PerformanceResourceTiming</a> objects in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a> of the relevant context. Resources that are
-    retrieved from <a href="http://www.w3.org/TR/html5/browsers.html#relevant-application-cache" title='relevant application cache'>relevant
-application caches</a> or local resources MUST be included
-    as <a href="#performanceresourcetiming">PerformanceResourceTiming</a> objects in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a> [[!performance-timeline]].
-</p>
+
+<p>All resources <a title='fetch' href="http://www.w3.org/TR/html5/infrastructure.html#fetch">fetched</a> by the current <a href="http://www.w3.org/TR/html5/browsers.html#browsing-context">browsing</a> [[!HTML5]] or worker [[!WORKERS]] context's MUST be included as <a href="#performanceresourcetiming">PerformanceResourceTiming</a> objects in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a> of the relevant context. Resources that are retrieved from <a href="http://www.w3.org/TR/html5/browsers.html#relevant-application-cache" title='relevant application cache'>relevant application caches</a> or local resources MUST be included as <a href="#performanceresourcetiming">PerformanceResourceTiming</a> objects in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a> ([[!performance-timeline]]). Resources for which the <a title='fetch' href="http://www.w3.org/TR/html5/infrastructure.html#fetch">fetch</a> was initiated, but was later aborted (e.g. due to a network error) MUST be included as <a href="#performanceresourcetiming">PerformanceResourceTiming</a> objects in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a> and MUST contain initialized attribute values for processed substeps of the <a href="#processing-model">processing model</a>.</p>
+
 <p>The rest of this section is non-normative.</p>
 <p>
     Examples:</p>
@@ -300,6 +297,12 @@ <h3>Resources Included in the <code><a href="#performanceresourcetiming">Perform
             be included as a <a href="#performanceresourcetiming">PerformanceResourceTiming</a> object in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a>.
 			By definition <code><a href="https://tools.ietf.org/html/rfc2397">data: URI</a></code> contains embedded data and does not require a <a href="http://www.w3.org/TR/html5/infrastructure.html#fetch">fetch</a>.
         </li>
+        <li>
+          If a resource <a href="http://www.w3.org/TR/html5/infrastructure.html#fetch">fetch</a> was aborted due to a networking error (e.g. DNS, TCP, or TLS error), then the fetch would be included as a <a href="#performanceresourcetiming">PerformanceResourceTiming</a> object in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a> with initialized attribute values up to the point of failure - e.g. a TCP handshake error should report DNS timestamps for the request, and so on.
+        </li>
+        <li>
+          If a resource <a href="http://www.w3.org/TR/html5/infrastructure.html#fetch">fetch</a> is aborted because it failed a fetch precondition (e.g. mixed content, CORS restriction, CSP policy, etc), then this resource will not be included as a <a href="#performanceresourcetiming">PerformanceResourceTiming</a> object in the <a href="http://www.w3.org/TR/performance-timeline/#sec-performance-timeline">Performance Timeline</a>.
+        </li>
     </ul>
 <p>
     The user agent MAY choose to limit how many resources are included as