Revert "Update the first letter when the first line is changed by adding a new text at its start."

This reverts commit 163903.
R=esprehn@chromium.org
BUG=92797

Review URL: https://codereview.chromium.org/102993011

git-svn-id: svn://svn.chromium.org/blink/trunk@164205 bbb929c8-8fbe-4397-9dbb-9b2b20218538