Fix surfaceflinger tests.

Update the screenshot code and add correct return values to surface flinger's
capturescreenshot function.

Buf: 18138368

Change-Id: Ieb42d289088589f941502fbd69da7aa939265e07
(cherry picked from commit 5a16a62950de06d48769e29f0c68a154ed7a7a89)
2 files changed