Enable expanding skipped lines even if 'Syntax Coloring' is off

On SideBySide diff UI if 'Syntax Coloring' is disabled attempting
to expand 'skipped common xx lines' will result in only one line
displaying on the left side. Enabling 'Syntax Coloring' makes the
expand work correctly on both sides.

This issue has existed since v2.3, as the server was not including
enough file content to support expanding the skipped regions.

Change-Id: I6f33b21415746a54c0cdc507246c139b49cd045d
2 files changed