surfaceflinger: Allow gpu to render widevine level3.

Allow gpu to render widevine level3 but keep
blocking screen shots.

CRs-fixed: 428647,424769,421767
Change-Id: I914232a062acbb7b17901dbf2b414973230e59d9

Conflicts:

	services/surfaceflinger/Layer.cpp
(cherry picked from commit f4c511eadf2450f1764617245205ffb940b710f8)
(cherry picked from commit 98d7ecf2a82fe6c2a82285b64ea9a8d8da443e9a)
(cherry picked from commit 2dcc6c014c7593d4d18667299718832a339905e3)
Revert "get rid of MemoryHeapPmem"

This reverts commit 7a7524810a0950c1c2b18014a8f1c637275165c4 and
makes MemoryHeapPmem conditioned to BOARD_NEEDS_MEMORYHEAPPMEM

Change-Id: I2f38340984ba87d6970d17ec944e3faded4132c8
ui/sf: Add support for exynos HDMI