calculatedLayoutDidChange may be called needlessly.

[Adlai-Holler]

If you have a node that participates in a layout transition, but whose layout doesn't change, it'll still get calculatedLayoutDidChange because _pendingLayoutTransitionDidComplete calls it unconditionally:

We should either:

• Not call _pendingLayoutTransitionDidComplete if there was no pending layout transition.
• Pass the nullable transition as an argument, and only call calculatedLayoutDidChange if it actually changed.