Revert "Preserve textarea state when building WikiEditor UI"

Sadly this caused bug 64289; so we're going to revert this for now;
then redeploy this and Ib97f47ef1d66420682bd429c9c12e66c3392e77d
in one of the swats next week.

This reverts commit effd98be7ebaa1f6f0d2c5b524c96ed6e0839a32.

Change-Id: Idde3e51e894f8c92f47fb06f0cf08d01e82ccb48
(cherry picked from commit 908e7cc56c4ef5db2ab0d213b2dbd8c8034a0da7)