Streamline cast certificate loading

This CL adds special code to create a session and sign a
message with an RSA key without initializing the full session.

This is to fix:
b/16130551 Molly does not show up in CAST device list

Change-Id: I4a14b312ef67e666c7c9504fe8135c6924be4c0d

libwvdrmengine/mediadrm/Android.mk

@@ -3,6 +3,7 @@ include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES := \
   src/WVDrmPlugin.cpp \
+  src/WVGenericCryptoInterface.cpp \
 
 LOCAL_C_INCLUDES := \
   bionic \