Show correct part of truncated text before ellipsis in contrary flow

When text is in a contrary-direction flow then ensure we show the start of the
text that we are truncating rather than the end of it.

BUG=155836

Review-Url: https://codereview.chromium.org/1916943002
Cr-Commit-Position: refs/heads/master@{#390874}
19 files changed