Stripping out whitespace for saved file but not for editor file.  First round (including mistakes I'll pull out in next commit).
Cleaned up for round 2.  Will attempt to relocate code to _replaceContents next
Relocated code to _replaceContents successfully.
Cleaned up
Moved writing to disk out of _replaceContents and into the file save logic.
Merge branch 'master' of https://github.com/dart-lang/spark into umop-settings-strip_whitespace-retain_cursor
Passing text to _stripWhitespace for clearer behavior
Review fix
Merge pull request #1695 from dart-lang/umop-settings-strip_whitespace-retain_cursor

Continue stripping trailing whitespace to file without affecting cursor