[RN] Disable filmstrip separation on Android

This zOrder change fixes the issue that the scrollable filmstrip videos
rendered in front of the local participant, however there is still an
issue that needs to be fixed later: The rendered videos should have
overflow: 'hidden' property applied so then they don't get rendered when
scrolled out of the ScrollView, that property however doesn't seem to
work for Video components.

react/features/filmstrip/components/native/Filmstrip.js

 import { ScrollView } from 'react-native';
 import { connect } from 'react-redux';
 
-import { Container } from '../../../base/react';
+import { Container, Platform } from '../../../base/react';
 import {
     isNarrowAspectRatio,
     makeAspectRatioAware
  * @extends Component
  */
 class Filmstrip extends Component<Props> {
+    /**
+     * Whether the local participant should be rendered separately from the
+     * remote participants i.e. outside of their {@link ScrollView}.
+     */
+    _separateLocalThumbnail: boolean;
+
+    /**
+     * Constructor of the component.
+     *
+     * @inheritdoc
+     */
+    constructor(props) {
+        super(props);
+
+        // XXX Our current design is to have the local participant separate from
+        // the remote participants. Unfortunately, Android's Video
+        // implementation cannot accommodate that because remote participants'
+        // videos appear on top of the local participant's video at times.
+        // That's because Android's Video utilizes EGL and EGL gives us only two
+        // practical layers in which we can place our participants' videos:
+        // layer #0 sits behind the window, creates a hole in the window, and
+        // there we render the LargeVideo; layer #1 is known as media overlay in
+        // EGL terms, renders on top of layer #0, and, consequently, is for the
+        // Filmstrip. With the separate LocalThumnail, we should have left the
+        // remote participants' Thumbnails in layer #1 and utilized layer #2 for
+        // LocalThumbnail. Unfortunately, layer #2 is not practical (that's why
+        // I said we had two practical layers only) because it renders on top of
+        // everything which in our case means on top of participant-related
+        // indicators such as moderator, audio and video muted, etc. For now we
+        // do not have much of a choice but to continue rendering LocalThumbnail
+        // as any other remote Thumbnail on Android.
+        this._separateLocalThumbnail = Platform.OS !== 'android';
+    }
+
     /**
      * Implements React's {@link Component#render()}.
      *
                 style = { filmstripStyle }
                 visible = { this.props._visible }>
                 {
-                    !isNarrowAspectRatio_ && <LocalThumbnail />
+                    this._separateLocalThumbnail
+                        && !isNarrowAspectRatio_
+                        && <LocalThumbnail />
                 }
                 <ScrollView
                     horizontal = { isNarrowAspectRatio_ }
                     showsHorizontalScrollIndicator = { false }
                     showsVerticalScrollIndicator = { false }
                     style = { styles.scrollView } >
+                    {
+                        !this._separateLocalThumbnail
+                            && !isNarrowAspectRatio_
+                            && <LocalThumbnail />
+                    }
                     {
                         /* eslint-disable react/jsx-wrap-multilines */
 
 
                         /* eslint-enable react/jsx-wrap-multilines */
                     }
+                    {
+                        !this._separateLocalThumbnail
+                            && isNarrowAspectRatio_
+                            && <LocalThumbnail />
+                    }
                 </ScrollView>
                 {
-                    isNarrowAspectRatio_ && <LocalThumbnail />
+                    this._separateLocalThumbnail
+                        && isNarrowAspectRatio_
+                        && <LocalThumbnail />
                 }
             </Container>
         );