Bug 1577467 - Remove obsolete iframe container for DevTools animation inspector; r=daisuke

The animation inspector is [loaded on demand by the inspector](https://searchfox.org/mozilla-central/rev/8ea946dcf51f0d6400362cc1d49c8d4808e`eacf1/devtools/client/inspector/inspector.js#937-942) as a sidebar panel via an `InspectorPanel` instance. The iframe container from index.xhtml seems to be a leftover from a time where the animation inspector was loaded differently.

No failing tests after removing iframe. Is this ok to cleanup?

Differential Revision: https://phabricator.services.mozilla.com/D43951

--HG--
extra : moz-landing-system : lando

devtools/client/inspector/components/InspectorTabPanel.css

@@ -2,12 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-.devtools-inspector-tab-frame {
-  border: none;
-  height: 100%;
-  width: 100%;
-}
-
 .devtools-inspector-tab-panel {
   width: 100%;
   height: 100%;

devtools/client/inspector/index.xhtml

@@ -139,10 +139,6 @@
           </div>
         </div>
       </div>
-
-      <div id="sidebar-panel-animationinspector" class="theme-sidebar inspector-tabpanel">
-        <iframe class="devtools-inspector-tab-frame"></iframe>
-      </div>
     </div>
 
   </div>

devtools/client/themes/inspector.css

@@ -191,9 +191,3 @@ iframe {
   height: 100%;
   width: 100%;
 }
-
-/* Animation inspector */
-#sidebar-panel-animationinspector {
-  height: 100%;
-  width: 100%;
-}