Convert editing/undo/4063751.html to use w3c test harness
This patch converts "editing/undo/4063751.html" to use w3c test harness
to simplify test script for improving readability.
This patch also renames it to "redo_rebalance_whitespace.html" to provide a
hint what this test script verifies.
BUG=n/a
TEST=n/a; no behavior changes
Committed:
https://crrev.com/14da44c0d317243b314d97b04b57b47c9888f127
Cr-Commit-Position: refs/heads/master@{#412749}