SF: Set crop for color layer in ChildColorLayerTest

When creating a color or container layer, the call will fail if a buffer size is set. Layers
without buffers should set a crop instead.

Test: mmma frameworks/native/services/surfaceflinger/tests/ && \
adb sync data && \
adb shell /data/nativetest64/sffakehwc_test/sffakehwc_test

Change-Id: I76cd85b43614cd0ef1113d127840f751a11cbb12