this allows the test to be sharded more efficiently and speeds up the
run when built with slower configs, e.g., asan.
Change-Id: If6d863b76871e3934704a1079bbf17f4886932c7
Move class VpxScaleBase to new file test/vpx_scale_test.h.
Add new file test/vp9_scale_test.cc with ScaleFrameTest.
BUG=webm:1419
Change-Id: Iec2098eafcef99b94047de525e5da47bcab519c1