Processing a manifest: Moved defaults into individual processing steps.

This keeps the relevant info about the default values of members closely
related to the other relevant material about that member. It's also
consistent with how the rest of the members (e.g. scope) treat default
values. And prevents possible errors where the incorrect default value
is used by an intermediate step in between assigning the default and
assigning the actual value.

index.html

@@ -502,6 +502,8 @@ <h3>
           |json:ordered map| and [=ordered map=] |manifest:ordered map|:
         </p>
         <ol class="algorithm">
+          <li>Set |manifest|["dir"] to "auto".
+          </li>
           <li>If |json|["dir"] doesn't [=map/exist=] or if |json|["dir"] is not
           a [=string=], return.
           </li>
@@ -679,6 +681,8 @@ <h3>
           |json:ordered map| and [=ordered map=] |manifest:ordered map|:
         </p>
         <ol class="algorithm">
+          <li>Set |manifest|["display"] to "browser".
+          </li>
           <li>If |json|["display"] doesn't [=map/exist=] or |json|["display"]
           is not a a [=string=], return.
           </li>
@@ -773,6 +777,8 @@ <h3>
           |manifest URL:URL|, and [=URL=] |document URL:URL|:
         </p>
         <ol class="algorithm">
+          <li>Set |manifest|["start_url"] to |document URL|.
+          </li>
           <li>If |json|["start_url"] doesn't [=map/exist=] or
           |json|["start_url"] is not a [=string=], return.
           </li>
@@ -784,8 +790,8 @@ <h3>
           </li>
           <li>If |start URL| is failure, return.
           </li>
-          <li>If |start URL| is not <a>same origin</a> as <var>document
-          URL</var>, return.
+          <li>If |start URL| is not <a>same origin</a> as |document URL|,
+          return.
           </li>
           <li>Otherwise, set |manifest|["start_url"] to |start URL|.
           </li>
@@ -1267,9 +1273,7 @@ <h3>
                 </li>
               </ol>
             </li>
-            <li>Let |manifest:ordered map| be a new [=ordered map=] «[
-            "display" → "browser", "dir" → "auto", "start_url" → |document URL|
-            ]».
+            <li>Let |manifest:ordered map| be an empty [=ordered map=].
             </li>
             <li>[=Process the `dir` member=] passing |json| and |manifest|.
             </li>