Widevine extractor changes to support secure media buffer playback.

Supports either secure or insecure buffer configurations, depending
on the build-time flag REQUIRE_SECURE_BUFFERS.

Change-Id: I5b8150315eced4ed9be656b73d91485a6216819d

proprietary/wvm/Android.mk

@@ -4,6 +4,8 @@ LOCAL_PATH := $(call my-dir)
 
 include $(CLEAR_VARS)
 
+LOCAL_CFLAGS := -DREQUIRE_SECURE_BUFFERS
+
 LOCAL_SRC_FILES:=           \
     WVMLogging.cpp          \
     WVMExtractorImpl.cpp    \