Remove chromium mode from skdiff, because it is no longer actively used. Ran tools/tests/run.sh to validate this change.
Remove chromium mode from skdiff, because it is no longer actively used.
Ran tools/tests/run.sh to validate this change.

TBR=caryclark1
Review URL: https://codereview.appspot.com/6222045

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia