Disallow explicitely non top-level browsing contexts (#610)

Author: beaufortfrancois

index.html

@@ -2311,6 +2311,11 @@ <h3><dfn>Writing content</dfn></h3>
           <li>
             Let |p:Promise| be a new {{Promise}} object.
           </li>
+          <li>
+            If not currently executing in the currently active <a>top-level
+            browsing context</a>, then reject |p| with and
+            {{"InvalidStateError"}} {{DOMException}} and return |p|.
+          </li>
           <li>
             Let |message:NDEFMessageSource| be the first argument.
           </li>
@@ -3409,6 +3414,11 @@ <h3><dfn>Writing content</dfn></h3>
           <li>
             Let |p:Promise| be a new {{Promise}} object.
           </li>
+          <li>
+            If not currently executing in the currently active <a>top-level
+            browsing context</a>, then reject |p| with and
+            {{"InvalidStateError"}} {{DOMException}} and return |p|.
+          </li>
           <li>
             Let |reader:NDEFReader| be the {{NDEFReader}} instance.
           </li>