Removing TimerMixin on SwipeableRow (#21499)

Summary:
Related to #21485.
Removed TimerMixin from the SwipeableRow component since it is currently not used.
Added a test case for `SwipeableRow` animation in the `SwipeableListViewSimpleExample`, by adding the `bounceFirstRowOnMount` prop, to check for any runtime issues with the setTimeout method.

- [x] `npm run prettier`
- [x] `npm run flow-check-ios`
- [x] `npm run flow-check-android`
- [x] runtime tests using `SwipeableFlatListExample` on Android and iOS
- [x] runtime tests using `SwipeableListViewSimpleExample` on Android and iOS

**RNTester steps**

- [x] Run RNTester.
- [x] Navigate to `SwipeableFlatListExample` and check if the `_animateBounceBack` animation executes when the `shouldBounceOnMount` props is passed.
- [x] Swipe the row and check if the events ran correctly
- [x] Navigate to `SwipeableListViewSimpleExample` and check if the `_animateBounceBack` animation executes when the `shouldBounceOnMount` props is passed.
- [x] Swipe the row and check if the events ran correctly

[GENERAL] [ENHANCEMENT] [Libraries/Experimental/SwipeableRow/SwipeableRow.js] - remove TimerMixin dependency
[GENERAL] [ENHANCEMENT] [RNTester/js/SwipeableListViewSimpleExample.js] - Add bounceFirstRowOnMount to guarantee the SwipeableRow correct behavior.
Pull Request resolved: https://github.com/facebook/react-native/pull/21499

Reviewed By: TheSavior

Differential Revision: D10218361

Pulled By: RSNara

fbshipit-source-id: c8e6d5ced4c1237e48bb4c43592016684b2c6360

Libraries/Experimental/SwipeableRow/SwipeableRow.js

@@ -16,10 +16,6 @@ const PanResponder = require('PanResponder');
 const React = require('React');
 const PropTypes = require('prop-types');
 const StyleSheet = require('StyleSheet');
-/* $FlowFixMe(>=0.54.0 site=react_native_oss) This comment suppresses an error
- * found when Flow v0.54 was deployed. To see the error delete this comment and
- * run Flow. */
-const TimerMixin = require('react-timer-mixin');
 const View = require('View');
 
 const createReactClass = require('create-react-class');
@@ -85,8 +81,7 @@ const SwipeableRow = createReactClass({
   displayName: 'SwipeableRow',
   _panResponder: {},
   _previousLeft: CLOSED_LEFT_POSITION,
-
-  mixins: [TimerMixin],
+  _timeoutID: (null: ?TimeoutID),
 
   propTypes: {
     children: PropTypes.any,
@@ -157,7 +152,7 @@ const SwipeableRow = createReactClass({
        * Do the on mount bounce after a delay because if we animate when other
        * components are loading, the animation will be laggy
        */
-      this.setTimeout(() => {
+      this._timeoutID = setTimeout(() => {
         this._animateBounceBack(ON_MOUNT_BOUNCE_DURATION);
       }, ON_MOUNT_BOUNCE_DELAY);
     }
@@ -173,6 +168,12 @@ const SwipeableRow = createReactClass({
     }
   },
 
+  componentWillUnmount() {
+    if (this._timeoutID != null) {
+      clearTimeout(this._timeoutID);
+    }
+  },
+
   render(): React.Element<any> {
     // The view hidden behind the main view
     let slideOutView;