Add isBuffer to SurfaceFrame

Add a boolean that tells if the SurfaceFrame is representing a buffer or
not. This makes it easy to debug lost/stuck frames in the pending
classification list. Also add a miniDump for SurfaceFrame to enable
debugging the lost frame.

Bug: 182214639
Test: Build and flash
Change-Id: I6ceef46887a021c2f36e76f37fab8368802465a4