Revert "Revert "Refactor TextLine class""

This reverts commit 3c097aa45e1fc8c03e09aea09a0dc3596b82c761.

Reason for revert: we thought this CL caused b/119659731 but apparently it is not.

Change-Id: Id375c4c8f2bffb7c42dc36bc053d536c6ea57a8d
2 files changed