Add initial CurveMeasure code

- This code is entirely private and is not being used by anything.

- In a future CL we will write a class that uses CurveMeasure to compute dash points. In order to determine whether CurveMeasure or PathMeasure should be faster, we need the dash info (the sum of the on/off intervals and how many there are)

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2187083002

Review-Url: https://codereview.chromium.org/2187083002
4 files changed