impl WorkingFormatCF::getFlags()

The only color filter flag is isAlphaUnchanged(), so since alpha is
unchanged through any working format transformation, we can just return
whatever flags the child filter claims.

Add a simple test.

Change-Id: I2ce0300d9db55f953660ed157510070755c4c677
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/370824
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
2 files changed