Make Request constructor more forgiving

Folks are using the Request constructor in unexpected ways and
therefore it is throwing in unexpected ways (in particular when mode is
“navigate” or when setting referrer to a cross-origin URL). This will
make it throw less, while not really being less useful.

Fixes #245.

Author: annevk

Overview.html

@@ -7,7 +7,7 @@
 
 <p><a class="logo" href="https://whatwg.org/"><img alt="WHATWG" height="100" src="https://resources.whatwg.org/logo-fetch.svg" width="100"></a>
 <h1 id="cors">Fetch</h1>
-<h2 class="no-num no-toc" id="living-standard-—-last-updated-15-september-2016">Living Standard — Last Updated 15 September 2016</h2>
+<h2 class="no-num no-toc" id="living-standard-—-last-updated-27-september-2016">Living Standard — Last Updated 27 September 2016</h2>
 
 <dl>
  <dt>Participate:
@@ -4710,8 +4710,8 @@ <h3 id="request-class"><span class="secno">6.3 </span>Request class</h3>
 
   <ol>
    <li><p>If <var>request</var>'s <a href="#concept-request-mode" title="concept-request-mode">mode</a> is
-   "<code title="">navigate</code>", <a class="external" data-anolis-spec="webidl" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> a
-   <code title="">TypeError</code>.
+   "<code title="">navigate</code>", then set it to "<code>same-origin</code>".
+   <!-- This works because we have reset request's client too. -->
 
    <li><p>Unset <var>request</var>'s <a href="#omit-origin-header-flag">omit-<code>Origin</code>-header flag</a>.
 
@@ -4745,25 +4745,29 @@ <h3 id="request-class"><span class="secno">6.3 </span>Request class</h3>
    <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-parser" title="concept-url-parser">parsing</a>
    <var>referrer</var> with <var>baseURL</var>.
 
-   <li><p>If <var>parsedReferrer</var> is failure,
-   <a class="external" data-anolis-spec="webidl" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> a <code title="">TypeError</code>.
-
-   <li><p>If <var>parsedReferrer</var>'s
-   <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#non-relative-flag">non-relative flag</a> is set,
-   <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-scheme" title="concept-url-scheme">scheme</a> is
-   "<code>about</code>", and
-   <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-path" title="concept-url-path">path</a> contains a single string
-   "<code>client</code>", set <var>request</var>'s
-   <a href="#concept-request-referrer" title="concept-request-referrer">referrer</a> to "<code>client</code>" and
-   terminate these substeps.
+   <li><p>If <var>parsedReferrer</var> is failure, then <a class="external" data-anolis-spec="webidl" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> a
+   <code title="">TypeError</code>.
 
-   <li><p>If <var>parsedReferrer</var>'s
-   <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-origin" title="concept-url-origin">origin</a> is not
-   <a class="external" data-anolis-spec="html" href="https://html.spec.whatwg.org/multipage/browsers.html#same-origin">same origin</a> with <var>origin</var>,
-   <a class="external" data-anolis-spec="webidl" href="https://heycam.github.io/webidl/#dfn-throw">throw</a> a <code title="">TypeError</code>.
+   <li>
+    <p>If one of the following conditions is true, then set <var>request</var>'s
+    <a href="#concept-request-referrer" title="concept-request-referrer">referrer</a> to "<code>client</code>":
+
+    <ul class="brief">
+     <li><var>parsedReferrer</var>'s <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#non-relative-flag">non-relative flag</a> is set,
+     <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-scheme" title="concept-url-scheme">scheme</a> is "<code>about</code>", and
+     <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-path" title="concept-url-path">path</a> contains a single string
+     "<code>client</code>".
+
+     <li><var>parsedReferrer</var>'s
+     <a class="external" data-anolis-spec="url" href="https://url.spec.whatwg.org/#concept-url-origin" title="concept-url-origin">origin</a> is not
+     <a class="external" data-anolis-spec="html" href="https://html.spec.whatwg.org/multipage/browsers.html#same-origin">same origin</a> with <var>origin</var>
+    </ul>
+    <!-- This can happen when you create a fresh request with values from an older request. Throwing
+         would be rather hostile as preventing it requires implementing the same-origin check in
+         developer space. -->
 
-   <li><p>Set <var>request</var>'s
-   <a href="#concept-request-referrer" title="concept-request-referrer">referrer</a> to <var>parsedReferrer</var>.
+   <li><p>Otherwise, set <var>request</var>'s <a href="#concept-request-referrer" title="concept-request-referrer">referrer</a>
+   to <var>parsedReferrer</var>.
   </ol>
 
  <li><p>If <var>init</var>'s <code title="">referrerPolicy</code> member is present, set

Overview.src.html

@@ -4640,8 +4640,8 @@ <h3>Request class</h3>
 
   <ol>
    <li><p>If <var>request</var>'s <span title=concept-request-mode>mode</span> is
-   "<code title>navigate</code>", <span data-anolis-spec=webidl>throw</span> a
-   <code title>TypeError</code>.
+   "<code title>navigate</code>", then set it to "<code>same-origin</code>".
+   <!-- This works because we have reset request's client too. -->
 
    <li><p>Unset <var>request</var>'s <span>omit-<code>Origin</code>-header flag</span>.
 
@@ -4675,25 +4675,29 @@ <h3>Request class</h3>
    <span data-anolis-spec=url title=concept-url-parser>parsing</span>
    <var>referrer</var> with <var>baseURL</var>.
 
-   <li><p>If <var>parsedReferrer</var> is failure,
-   <span data-anolis-spec=webidl>throw</span> a <code title>TypeError</code>.
-
-   <li><p>If <var>parsedReferrer</var>'s
-   <span data-anolis-spec=url>non-relative flag</span> is set,
-   <span data-anolis-spec=url title=concept-url-scheme>scheme</span> is
-   "<code>about</code>", and
-   <span data-anolis-spec=url title=concept-url-path>path</span> contains a single string
-   "<code>client</code>", set <var>request</var>'s
-   <span title=concept-request-referrer>referrer</span> to "<code>client</code>" and
-   terminate these substeps.
+   <li><p>If <var>parsedReferrer</var> is failure, then <span data-anolis-spec=webidl>throw</span> a
+   <code title>TypeError</code>.
 
-   <li><p>If <var>parsedReferrer</var>'s
-   <span data-anolis-spec=url title=concept-url-origin>origin</span> is not
-   <span data-anolis-spec=html>same origin</span> with <var>origin</var>,
-   <span data-anolis-spec=webidl>throw</span> a <code title>TypeError</code>.
+   <li>
+    <p>If one of the following conditions is true, then set <var>request</var>'s
+    <span title=concept-request-referrer>referrer</span> to "<code>client</code>":
+
+    <ul class=brief>
+     <li><var>parsedReferrer</var>'s <span data-anolis-spec=url>non-relative flag</span> is set,
+     <span data-anolis-spec=url title=concept-url-scheme>scheme</span> is "<code>about</code>", and
+     <span data-anolis-spec=url title=concept-url-path>path</span> contains a single string
+     "<code>client</code>".
+
+     <li><var>parsedReferrer</var>'s
+     <span data-anolis-spec=url title=concept-url-origin>origin</span> is not
+     <span data-anolis-spec=html>same origin</span> with <var>origin</var>
+    </ul>
+    <!-- This can happen when you create a fresh request with values from an older request. Throwing
+         would be rather hostile as preventing it requires implementing the same-origin check in
+         developer space. -->
 
-   <li><p>Set <var>request</var>'s
-   <span title=concept-request-referrer>referrer</span> to <var>parsedReferrer</var>.
+   <li><p>Otherwise, set <var>request</var>'s <span title=concept-request-referrer>referrer</span>
+   to <var>parsedReferrer</var>.
   </ol>
 
  <li><p>If <var>init</var>'s <code title>referrerPolicy</code> member is present, set