[mobar] Fix shrinking text when using floating keyboard

In this scenario, we attempt to show the mini origin bar before bailing
out shortly afterwards. This is because we still get an insets animation
signal despite the start and end state being 0. This is out of our
control and can't be detected until it's too late (onStart), but we can
bail out slightly sooner.

To address the actual text shrinkage, we need to fix
enforceMaxTextHeight, which functions incorrectly if height and padding
change simultaneously. The height change needs a layout pass to get
committed, but the padding change is immediately reflected. The
resulting height calculation is wrong, causing us to over-shrink the
text due to a mistakenly small height. We can resolve this by deferring
the calculation until layout is no longer requested.

Bug: 434237090
Change-Id: If663874359411fe5181cd5a921b039e8062c8a11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6785640
Commit-Queue: Patrick Noland <pnoland@chromium.org>
Reviewed-by: Tomasz Wiszkowski <ender@google.com>
Cr-Commit-Position: refs/heads/main@{#1492299}