HWC2On1: Fall back to GLES for SolidColor

Even though SolidColor layers map cleanly to HWC_BACKGROUND composition
in HWC1, SurfaceFlinger never used HWC_BACKGROUND, so we can't trust
that HWC1 devices implemented it correctly. To preserve backwards
compatibility, this changes the behavior to fall back to client
composition to minimize incompatibilities with existing devices.

Bug: 30479781
Change-Id: I638339062e03f2c057b3e1624e7157587ddee7ec
1 file changed