Unbreak custom animated components

Summary:
Commit https://github.com/facebook/react-native/commit/c9960817eea008b2703657066212002557e0d939 broke `Animated.createAnimatedComponent()` for most components outside of the standard ones. This is because it will throw an exception for any component without a `viewConfig` defined, which basically no composition style component has AFAIK.

Related issues: https://github.com/facebook/react-native/issues/10825, https://github.com/oblador/react-native-vector-icons/issues/337, https://github.com/oblador/react-native-animatable/issues/70

This PR removes the check which is more treating the symptoms really – but shouldn't `setNativeProps` duck typing be enough?
Closes https://github.com/facebook/react-native/pull/10827

Differential Revision: D4178183

Pulled By: ericvicenti

fbshipit-source-id: b85cc78ed6d84dada4d476caa243332eaadb003f

Libraries/Animated/src/AnimatedImplementation.js

@@ -1735,12 +1735,6 @@ function createAnimatedComponent(Component: any): any {
       var callback = () => {
         if (this._component.setNativeProps) {
           if (!this._propsAnimated.__isNative) {
-            if (this._component.viewConfig == null) {
-              var ctor = this._component.constructor;
-              var componentName = ctor.displayName || ctor.name || '<Unknown Component>';
-              throw new Error(componentName + ' "viewConfig" is not defined.');
-            }
-
             this._component.setNativeProps(
               this._propsAnimated.__getAnimatedValue()
             );

Libraries/Renderer/src/renderers/native/NativeMethodsMixin.js

@@ -139,6 +139,12 @@ var NativeMethodsMixin = {
    * Manipulation](docs/direct-manipulation.html)).
    */
   setNativeProps: function(nativeProps: Object) {
+    if (!this.viewConfig) {
+      var ctor = this.constructor;
+      var componentName = ctor.displayName || ctor.name || '<Unknown Component>';
+      invariant(false, componentName + ' "viewConfig" is not defined.');
+    }
+
     if (__DEV__) {
       warnForStyleProps(nativeProps, this.viewConfig.validAttributes);
     }