Previously in Polygerrit, diff views were always displayed in the width
specified in diff preferences. This change gives the option to wrap
lines instead, which takes precedence over column width (the column
width option is hidden when line wrapping is selected), and fits the
diff view to screen.
The gerrit API already supports the 'lineWrapping' preference so this
change uses that already existing option.
Feature: Issue 4809
Change-Id: I0d9e292739b5910abfd04af63ec4c745bf06e446