Simplify condition in ShouldDecideStroke

Currently, the condition is complicated. In reality, the requirement is
that the number of samples is exactly equal to max.

Update the code so that it's clear.

Bug: b/240168494
Test: autoninja -C out/Default events_unittests
Change-Id: I8cdcdacc4cf9926779b22a47b7be62899c101702
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3854946


Reviewed-by: Rob Schonberger <robsc@chromium.org>
Auto-Submit: Siarhei Vishniakou <svv@google.com>
Commit-Queue: Siarhei Vishniakou <svv@google.com>
Cr-Commit-Position: refs/heads/main@{#1039304}