Ignore width of trailing whitespace for computing ellipsis

We used the full width of a line, including trailing spaces, to compute
ellipsis, sometimes causing spurious ellipsization when the space pushed
it past the layout width. This patch uses only the width up to the last
graphing character.

Fix for bug 17186801 "First line of title text is getting truncated even
if there's space on second line"

Change-Id: I49d07c18c8dd1d3b279f591224d23e10645dc8c0