remove dead code

remove dead code

Use code coverage and a new '-c' flag to find
and remove unneeded code.

TBR=reed@google.com

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2397593002

patch from issue 2397593002 at patchset 1 (http://crrev.com/2397593002#ps1)

Change-Id: I741a82de9191146c10457d4c0b9cb9605dff2069
Reviewed-on: https://skia-review.googlesource.com/2983
Reviewed-by: Cary Clark <caryclark@google.com>