SF: Extract CommitAndCompositeTest helper

Tests that TestableSurfaceFlinger::commitAndComposite can reuse this.

Fixes: 280430069
Test: SurfaceFlingerPowerHintTest
Test: SurfaceFlingerGetDisplayStatsTest
Change-Id: Ifc222d8433238ceee276aa16a2c67c222debe90e
3 files changed