[RN] aspect-ratio: preserve mode when width === height

If the view gets resized to a 1:1 aspect ratio, remember the previous mode to
avoid flickering when going back to a larger size or different aspect ratio.

react/features/base/aspect-ratio/actions.js

 import { SET_ASPECT_RATIO } from './actionTypes';
 import { ASPECT_RATIO_NARROW, ASPECT_RATIO_WIDE } from './constants';
 
+import type { Dispatch } from 'redux';
+
 /**
  * Sets the aspect ratio of the app's user interface based on specific width and
  * height.
  * @param {number} width - The width of the app's user interface.
  * @param {number} height - The height of the app's user interface.
  * @returns {{
- *      type: SET_ASPECT_RATIO,
- *      aspectRatio: Symbol
+ *     type: SET_ASPECT_RATIO,
+ *     aspectRatio: Symbol
  * }}
  */
 export function setAspectRatio(width: number, height: number): Object {
-    return {
-        type: SET_ASPECT_RATIO,
-        aspectRatio: width < height ? ASPECT_RATIO_NARROW : ASPECT_RATIO_WIDE
+    return (dispatch: Dispatch<*>, getState: Function) => {
+        // Don't change the aspect ratio if width and height are the same, that
+        // is, if we transition to a 1:1 aspect ratio.
+        if (width !== height) {
+            const aspectRatio
+                = width < height ? ASPECT_RATIO_NARROW : ASPECT_RATIO_WIDE;
+
+            if (aspectRatio
+                    !== getState()['features/base/aspect-ratio'].aspectRatio) {
+                return dispatch({
+                    type: SET_ASPECT_RATIO,
+                    aspectRatio
+                });
+            }
+        }
     };
 }