Bug 552811 - [TextViewer] shift left broken for mixed lines if empty
prefix is allowed

Empty strings are treated differently by MultiStringMatcher and
TextUtilities.indexOf() and needs to be handled specially now.

Fixup for c89b823822e2d73ba4996ad419475db34c916ed5.

Change-Id: Ifdb5c495f5fc99d33da6d879f436a37063b93430
2 files changed