New ReactShallowRenderer implementation

Replaced shallow renderer based on test renderer with a custom, isolated implementation that's stack and fiber compatible

scripts/fiber/tests-passing.txt

@@ -1560,6 +1560,7 @@ src/renderers/dom/shared/wrappers/__tests__/ReactDOMTextarea-test.js
 * should warn if value and defaultValue are specified
 
 src/renderers/dom/test/__tests__/ReactTestUtils-test.js
+* should only render 1 level deep
 * should have shallow rendering
 * should shallow render a functional component
 * should throw for invalid elements
@@ -1573,6 +1574,7 @@ src/renderers/dom/test/__tests__/ReactTestUtils-test.js
 * can setState in componentWillMount when shallow rendering
 * can pass context when shallowly rendering
 * can fail context when shallowly rendering
+* should warn about propTypes (but only once)
 * can scryRenderedDOMComponentsWithClass with TextComponent
 * can scryRenderedDOMComponentsWithClass with className contains \n
 * can scryRenderedDOMComponentsWithClass with multiple classes

src/isomorphic/classic/element/ReactElement.js

@@ -162,13 +162,6 @@ var ReactElement = function(type, key, ref, self, source, owner, props) {
  writable: false,
  value: source,
  });
- // _owner attribute would break shallow renderer equality checks.
- Object.defineProperty(element, '_owner', {
- configurable: false,
- enumerable: false,
- writable: false,
- value: owner,
- });
  } else {
  element._store.validated = false;
  element._self = self;