Don’t add onclick listener to React root

Fixes #13777

As part of #11927 we introduced a regression by adding onclick handler
to the React root as well. This causes the whole React tree to flash
when tapped on iOS devices (for reasons I outlined in #12989 (comment)).

To fix this, we should only apply onclick listeners to portal roots. I
verified that this fix indeed worked by checkout out our DOM fixtures
and added regression tests as well.

Strangely, I had to make changes to the DOM fixtures to see the behavior
in the first place. This seems to be caused by our normal sites being
bigger than the viewport:

![](http://cl.ly/3f18f8b85e91/Screen%20Recording%202018-10-05%20at%2001.32%20AM.gif)

An alternative fix would be to add a third parameter to
`appendChildToContainer` based on the tag of the parent fiber. Although
I think relying on the `_reactRootContainer` property that we set on the
element is less intrusive.

packages/react-dom/src/__tests__/ReactDOMComponent-test.js

@@ -2659,4 +2659,41 @@ describe('ReactDOMComponent', () => {
       document.body.removeChild(container);
     }
   });
+
+  describe('iOS Tap Highlight', () => {
+    it('adds onclick handler to elements with onClick prop', () => {
+      const container = document.createElement('div');
+
+      const elementRef = React.createRef();
+      function Component() {
+        return <div ref={elementRef} onClick={() => {}} />;
+      }
+
+      ReactDOM.render(<Component />, container);
+      expect(typeof elementRef.current.onclick === 'function').toBeTruthy();
+    });
+
+    it('adds onclick handler to a portal root', () => {
+      const container = document.createElement('div');
+
+      function Component() {
+        return <div onClick={() => {}} />;
+      }
+
+      ReactDOM.render(<Component />, container);
+      expect(typeof container.onclick === 'function').toBeFalsy();
+    });
+
+    it('does not add onclick handler to react root', () => {
+      const container = document.createElement('div');
+      const portalContainer = document.createElement('div');
+
+      function Component() {
+        return ReactDOM.createPortal(<div onClick={() => {}} />, portalContainer);
+      }
+
+      ReactDOM.render(<Component />, container);
+      expect(typeof portalContainer.onclick === 'function').toBeTruthy();
+    });
+  });
 });

packages/react-dom/src/client/ReactDOMHostConfig.js

@@ -360,7 +360,7 @@ export function appendChildToContainer(
   // event exists. So we wouldn't see it and dispatch it.
   // This is why we ensure that containers have inline onclick defined.
   // https://github.com/facebook/react/issues/11918
-  if (parentNode.onclick === null) {
+  if (!container._reactRootContainer && parentNode.onclick === null) {
     // TODO: This cast may not be sound for SVG, MathML or custom elements.
     trapClickOnNonInteractiveElement(((parentNode: any): HTMLElement));
   }