Fire AnimatedValue.stopAnimation callback with correct native value

Summary:
AnimatedValue fires a callback with the current value (raw value + offset) after calling it's `stopAnimation` method. The `_value` field on the `AnimatedValue` node is not necessarily kept in sync with the NativeAnimated value node, so the value provided to the callback may be out of sync.

This change checks if the `AnimatedValue` is a native node and passes the callback to the `NativeAnimatedAPI.getValue` callback, defaulting to the previous current JS node state if the node is not native.

Changelog:
[General][Fixed] - AnimatedValue.stopAnimation callback with correct value for NativeAnimated

Reviewed By: yungsters

Differential Revision: D32968572

fbshipit-source-id: b83f86eabe5456f762a15bc29cacb43f84513f6c

Libraries/Animated/__tests__/AnimatedNative-test.js

@@ -928,6 +928,30 @@ describe('Native Animated', () => {
       animation.stop();
       expect(NativeAnimatedModule.stopAnimation).toBeCalledWith(animationId);
     });
+
+    it('calls stopAnimation callback with native value', () => {
+      NativeAnimatedModule.getValue = jest.fn((tag, saveCallback) => {
+        saveCallback(1);
+      });
+
+      const anim = new Animated.Value(0);
+      Animated.timing(anim, {
+        duration: 1000,
+        useNativeDriver: true,
+      }).start();
+
+      const tag = anim.__getNativeTag();
+
+      let currentValue = 0;
+      anim.stopAnimation(value => (currentValue = value));
+
+      expect(NativeAnimatedModule.getValue).toBeCalledWith(
+        tag,
+        expect.any(Function),
+      );
+
+      expect(currentValue).toEqual(1);
+    });
   });
 
   describe('Animated Components', () => {

Libraries/Animated/nodes/AnimatedValue.js

@@ -186,7 +186,13 @@ class AnimatedValue extends AnimatedWithChildren {
     this.stopTracking();
     this._animation && this._animation.stop();
     this._animation = null;
-    callback && callback(this.__getValue());
+    if (callback) {
+      if (this.__isNative) {
+        NativeAnimatedAPI.getValue(this.__getNativeTag(), callback);
+      } else {
+        callback(this.__getValue());
+      }
+    }
   }
 
   /**