increase coverage of SkPath.cpp, remove unused code

Using Mike Klein's excellent coverage tool, increase the
unit testing of SkPath.cpp from 70% to 95%.

Along the way, determined that these functions were not
maintained or used:

SkPath::pathTo
SkPath::contains

as well as a large block of SkPath::cheapGetDirection().

Changed SkPath::validate() to permit infinities in
the path data points.

Fixed errors in preserving direction.
Fixed error setting direction when convexity is unknown.

Added missing conic to moveTo only detector.

BUG=
R=bsalomon@google.com, reed@google.com

Author: caryclark@google.com

Review URL: https://codereview.chromium.org/65493004

git-svn-id: http://skia.googlecode.com/svn/trunk/src@12291 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed