the core screenshot function now can capture the screen at any lower resolution
performing bilinear filtering.
we also now have some client code to interface with the screenshot service.
it's now possible to request a screenshot at a lower resolution.
Change-Id: I5a3b0e431421800e3aad601d9af8f94adffbc71f
screenshots are taken using ISurfaceComposer::captureScreen() which returns
the size of the screenshot and an IMemoryHeap containing the data.
screenshots have limitations:
- they will always fail if a secure window is up on screen
- require GL_OES_framebuffer_object extension
- in some situation, video planes won't been captured
Change-Id: I741c68a2d2984fb139039301c3349e6780e2cd58
