dillon1000/react

Strict mode and default mode should have same Suspense semantics (#13882)

In the default mode, Suspense has special semantics where, in
addition to timing out immediately, we don't unwind the stack before
rendering the fallback. Instead, we commit the tree in an inconsistent
state, then synchronous render *again* to switch to the fallback. This
is slower but is less likely to cause issues with older components that
perform side effects in the render phase (e.g. componentWillMount,
componentWillUpdate, and componentWillReceiveProps).

We should do this in strict mode, too, so that there are no semantic
differences (in prod, at least) between default mode and strict mode.
The rationale is that it makes it easier to wrap a tree in strict mode
and start migrating components incrementally without worrying about new
bugs in production.