Use boolean assertion for documentMode check

[aweary]

Resolves #10030

Reverts a small change made in #8575. This should be safe, as we still use this assertion for the change event bubbling check.

cc @flarnie @gaearon this will require another 15.6.x release (not sure if one was planned)

[aweary]

This change was already made in master as well: #7594 It just wasn't included in the backport.

[gaearon]

Why does #7594 change two lines but this PR changes one?

[aweary]

That second line is already using !document.documentMode

[gaearon]

Mind creating an issue linking to everything that's still necessary for 15.6.x? Another one I'm thinking about is CurrentOwner bugfix.

[gaearon]

Need to run prettier?

[aweary]

@gaearon is the 15.6-dev branch meant to be working with prettier? I did run it locally but it was really out of sync, making the following changes:

	modified:   addons/create-react-class/test.js
	modified:   addons/react-addons-create-fragment/test.js
	modified:   addons/react-addons-linked-state-mixin/test.js
	modified:   addons/react-addons-pure-render-mixin/test.js
	modified:   addons/react-addons-shallow-compare/test.js
	modified:   addons/react-addons-update/test.js
	modified:   addons/react-linked-input/test.js
	modified:   src/renderers/dom/ReactDOM.js
	modified:   src/renderers/dom/client/ReactBrowserEventEmitter.js
	modified:   src/renderers/dom/client/ReactMount.js
	modified:   src/renderers/dom/client/syntheticEvents/SyntheticWheelEvent.js
	modified:   src/renderers/dom/shared/DOMProperty.js
	modified:   src/renderers/dom/shared/ReactComponentBrowserEnvironment.js
	modified:   src/renderers/dom/shared/hooks/ReactDOMUnknownPropertyHook.js
	modified:   src/renderers/native/ReactNative.js
	modified:   src/renderers/native/ReactNativeComponentEnvironment.js
	modified:   src/renderers/shared/ReactDebugTool.js
	modified:   src/renderers/shared/fiber/__tests__/ReactCoroutine-test.js
	modified:   src/renderers/shared/hooks/__tests__/ReactHostOperationHistoryHook-test.js
	modified:   src/renderers/shared/stack/event/eventPlugins/ResponderEventPlugin.js
	modified:   src/renderers/shared/stack/event/eventPlugins/TouchHistoryMath.js
	modified:   src/renderers/shared/stack/event/eventPlugins/__tests__/ResponderEventPlugin-test.js
	modified:   src/renderers/shared/stack/reconciler/ReactOwner.js
	modified:   src/renderers/shared/stack/reconciler/__tests__/ReactIdentity-test.js
	modified:   src/renderers/shared/utils/Transaction.js
	modified:   src/renderers/testing/ReactShallowRenderer.js
	modified:   src/test/ReactTestUtils.js

I can commit these changes (in a separate PR probably) if you'd like @gaearon

[gaearon]

Hmm. It used to work but maybe we're not yet using Yarn there so we need to cherry-pick #10038?

[aweary]

@gaearon cherry-picking #10038 doesn't seem to resolve it.

[nhunzaker]

I think we might have gotten a false positive on the commit where we first ran prettier. I just re-ran the build without cache and it looks like the prettier step failed:

https://circleci.com/gh/facebook/react/4254

It's hard to tell what version of prettier ran - possibly 1.4 - but do you think we just need to run prettier 1.2.2.0 again on 15.6-dev as @aweary suggested?

[gaearon]

I'm cool either way, let's just get the branch to be green.

[aweary]

cc @gaearon @nhunzaker CI is now green 🎉