When setting paint color/alpha, pin alpha to [0,1]

We used to just assert, but it turns out that Android has tests that
explicitly set out-of-range alpha values (and disable our asserts).

Bug: skia:11942
Bug: b/186543004
Change-Id: I167de7aba261ca3df579f9a0bddb0d90605e0094
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/465381
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed