Check doc fully active during response.complete() (#748)

* Check doc fully active during response.complete()

Author: marcoscaceres

index.html

@@ -3526,13 +3526,32 @@ 
           <li>Return <var>promisevar> and perform the remaining steps <a>in
           parallela>.
           li>
-          <li>Close down any remaining user interface. The <a>user agenta>
-          MAY use the value <var>resultvar> to influence the user experience.
-          li>
-          <li>Set the <a>user agenta>'s <a>payment request is showinga>
-          boolean to false.
+          <li>If <var>documentvar> stops being <a data-cite=
+          "!HTML#fully-active">fully activea> while the user interface is
+          being shown, or no longer is by the time this step is reached, then:
+            <ol>
+              <li>Close down the user interface.
+              li>
+              <li>Set the <a>user agenta>'s <a>payment request is showinga>
+              boolean to false.
+              li>
+              <li>Reject <var>promisevar> with an "<a>AbortErrora>"
+              <a>DOMExceptiona>.
+              li>
+            ol>
           li>
-          <li>Resolve <var>promisevar> with undefined.
+          <li>Otherwise:
+            <ol>
+              <li>Close down any remaining user interface. The <a>user
+              agenta> MAY use the value <var>resultvar> to influence the
+              user experience.
+              li>
+              <li>Set the <a>user agenta>'s <a>payment request is showinga>
+              boolean to false.
+              li>
+              <li>Resolve <var>promisevar> with undefined.
+              li>
+            ol>
           li>
         ol>
       section>