Allow screenshot to carry more information.

Previously screenshot returns a GraphicBuffer without any other information
about how to interpret this buffer, especially color space. We could not take
any WCG screenshot, and the color space information is also lost by the time we
create bitmap from the GraphicBuffer. This patch adds a ScreenshotGraphicBuffer
as a wrapper around GraphicBuffer with more information, for example color
space. And make screenshot native method return ScreenshotGraphicBuffer.

BUG: 116112787
Test: Build, flash and boot. Verify with WCG Photos.
Change-Id: I03cc5ce76d13f165c1203ced0b7fefc570dd2096