Previously, this threw:
```
FAIL src/test/__tests__/ReactTestUtils-test.js (7.291s)
● ReactTestUtils › it can fail context when shallowly rendering
- TypeError: Cannot read property '_source' of null
at describeID (src/renderers/shared/devtools/ReactComponentTreeDevtool.js:70:46)
at Object.ReactComponentTreeDevtool.getStackAddendumByID (src/renderers/shared/devtools/ReactComponentTreeDevtool.js:203:15)
at checkReactTypeSpec (src/isomorphic/classic/types/checkReactTypeSpec.js:76:58)
at ReactCompositeComponentMixin._checkContextTypes (src/renderers/shared/stack/reconciler/ReactCompositeComponent.js:668:5)
at ReactCompositeComponentMixin._processContext (src/renderers/shared/stack/reconciler/ReactCompositeComponent.js:607:14)
at ReactCompositeComponentMixin.mountComponent (src/renderers/shared/stack/reconciler/ReactCompositeComponent.js:191:30)
at ReactShallowRenderer._render (src/test/ReactTestUtils.js:483:14)
at _batchedRender (src/test/ReactTestUtils.js:460:12)
at ReactDefaultBatchingStrategyTransaction.Mixin.perform (src/shared/utils/Transaction.js:140:20)
at Object.ReactDefaultBatchingStrategy.batchedUpdates (src/renderers/shared/stack/reconciler/ReactDefaultBatchingStrategy.js:65:19)
at Object.batchedUpdates (src/renderers/shared/stack/reconciler/ReactUpdates.js:112:20)
at ReactShallowRenderer.render (src/test/ReactTestUtils.js:453:16)
at Spec.eval (src/test/__tests__/ReactTestUtils-test.js:289:34)
at jasmine.Block.execute (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:1067:17)
at jasmine.Queue.next_ (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2100:31)
at jasmine.Queue.start (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2053:8)
at Spec.jasmine.Spec.execute (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2380:14)
at jasmine.Queue.next_ (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2100:31)
at onComplete (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2096:18)
at Spec.jasmine.Spec.finish (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2354:5)
at eval [as onComplete] (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2381:10)
at jasmine.Queue.next_ (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2110:14)
at eval (node_modules/jest-jasmine1/vendor/jasmine-1.3.0.js:2090:18)
at Timeout.e [as _onTimeout] (node_modules/jsdom/lib/jsdom/browser/Window.js:440:19)
at tryOnTimeout (timers.js:224:11)
at Timer.listOnTimeout (timers.js:198:5)
```
* Don't count the time inside flushes towards lifecycle hooks
Fixes#6842.
We keep the existing behavior of testing for matching `onBeginLifeCycleTimer`/`onEndLifeCycleTimer` calls, but we push the current timer onto the stack if we enter a flush.
This solves an issue with portals which cause updates while a lifecycle timer is already running.
I chose to subtract the time spent in the flush from the time counted towards the lifecycle method because it would artificially inflate the “total” time of the component due to all the components inside the portal, so it would skew the exclusive table.
* Fix up the comment
This helps us make sure we don't break React ART in a minor or patch release. The idea is to not change these files when making minor or patch changes. Copied directly from react-art with requires fixed. (I also picked a different haste name just in case.)
* Fix componentWillUnmount() not counted by ReactPerf
* Test that functional component render() time shows up in ReactPerf
* Test for setState() code path updates being included
* Update shallowCompare to accept nextContext
Across our application we are using immutable objects as properties and thus using shallowCompare for all our {{shouldComponentUpdate}}. Because of this children with contextTypes don't get updates when the context on the parent changes. Adding an additional comparison for context (when it is provided) fixes this problem.
* Remove the undefined check
* Add nextContext
This adds some tests for getElement() and verifies that it works for text components too.
The code that calls the instrumentation is fixed where necessary so that the tests pass.
We extract common logic between DOM and native tests so they don't diverge.
Also, rather than build a tree object in advance for testing, we will walk the tree on the go.
This lets us have much more specific error messages with a clear path when something goes wrong.
Test Plan: Changed the preprocessor to log the output of babel.transform and saw
```
var _jsxFileName = 'src/isomorphic/modern/element/__tests__/ReactJSXElementValidator-test.js';
```
in the resulting output, instead of an absolute path.