Use response's internal response at end of fetch handover

This ensures that callers of processResponseEndOfBody and processResponseConsumeBody receive the correct body and response without additional steps.

Closes #1512.

fetch.bs

@@ -4817,7 +4817,11 @@ steps:
  <a for="fetch params">process response</a> given <var>response</var>, with <var>fetchParams</var>'s
  <a for="fetch params">task destination</a>.
 
- <li><p>If <var>response</var>'s <a for=response>body</a> is null, then run
+ <li><p>Let <var>internalResponse</var> be <var>response</var>, if <var>response</var> is a
+ <a>network error</a>; otherwise <var>response</var>'s
+ <a for="filtered response">internal response</a>.
+
+ <li><p>If <var>internalResponse</var>'s <a for=response>body</a> is null, then run
  <var>processResponseEndOfBody</var>.
 
  <li>
@@ -4835,8 +4839,8 @@ steps:
    <a for="TransformStream/set up"><i>flushAlgorithm</i></a> set to
    <var>processResponseEndOfBody</var>.
 
-   <li><p>Set <var>response</var>'s <a for=response>body</a>'s <a for=body>stream</a> to the result
-   of <var>response</var>'s <a for=response>body</a>'s <a for=body>stream</a>
+   <li><p>Set <var>internalResponse</var>'s <a for=response>body</a>'s <a for=body>stream</a> to the
+   result of <var>internalResponse</var>'s <a for=response>body</a>'s <a for=body>stream</a>
    <a for=ReadableStream>piped through</a> <var>transformStream</var>.
   </ol>
 
@@ -4850,18 +4854,19 @@ steps:
   <ol>
    <li><p>Let <var>processBody</var> given <var>nullOrBytes</var> be this step: run
    <var>fetchParams</var>'s <a for="fetch params">process response consume body</a> given
-   <var>response</var> and <var>nullOrBytes</var>.
+   <var>internalResponse</var> and <var>nullOrBytes</var>.
 
    <li><p>Let <var>processBodyError</var> be this step: run <var>fetchParams</var>'s
-   <a for="fetch params">process response consume body</a> given <var>response</var> and failure.
+   <a for="fetch params">process response consume body</a> given <var>internalResponse</var> and
+   failure.
 
-   <li><p>If <var>response</var>'s <a for=response>body</a> is null, then <a>queue a fetch task</a>
-   to run <var>processBody</var> given null, with <var>fetchParams</var>'s
+   <li><p>If <var>internalResponse</var>'s <a for=response>body</a> is null, then
+   <a>queue a fetch task</a> to run <var>processBody</var> given null, with <var>fetchParams</var>'s
    <a for="fetch params">task destination</a>.
 
-   <li><p>Otherwise, <a for=body>fully read</a> <var>response</var>'s <a for=response>body</a> given
-   <var>processBody</var>, <var>processBodyError</var>, and <var>fetchParams</var>'s
-   <a for="fetch params">task destination</a>.
+   <li><p>Otherwise, <a for=body>fully read</a> <var>internalResponse</var>'s
+   <a for=response>body</a> given <var>processBody</var>, <var>processBodyError</var>, and
+   <var>fetchParams</var>'s <a for="fetch params">task destination</a>.
   </ol>
 </ol>
 </div>
@@ -8812,8 +8817,16 @@ particular at what stage you would like to receive a callback:
    <a for=response>body</a> failed, e.g., due to an I/O error.
 
    <dt>a <a>byte sequence</a>
-   <dd><a for=body>Fully reading</a> the contents of the <a for=/>response</a>'s
-   <a for=response>body</a> succeeded.
+   <dd>
+    <p><a for=body>Fully reading</a> the contents of the <a for=/>response</a>'s
+    <a for=response>body</a> succeeded.
+
+    <p class=warning>A <a>byte sequence</a> containing the full contents will be passed also for a
+    <a for=/>request</a> whose <a for=request>mode</a> is "<code>no-cors</code>". Callers have to
+    be careful when handling such content, as it should not be accessible to the requesting
+    <a for=/>origin</a>. For example, the caller may use contents of a "<code>no-cors</code>"
+    <a for=/>response</a> to display image contents directly to the user, but those image contents
+    should not be directly exposed to scripts in the embedding document.
   </dl>
 
   <div id=example-callback-upon-completion class=example>