Update SampleAndroidShadows to use algorithm closer to Android OpenGL

Includes:
* Update light position to be at a similar distance to Android OS
* Scale spot shadows correctly
* Compute stroke shapes and radii correctly
* Allow for larger blur radius for shadows

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2319003003
TBR=reed@google.com
NOTRY=true
NOTREECHECKS=true

Review-Url: https://codereview.chromium.org/2319003003
3 files changed