Added a test_mode flag to the libwvdrmengine plugin to support verifying decryption results. Change-Id: I9edbd6279d54fc495b5bbad8273c179106cad474
Builds libwvmdrmengine.so, which is loaded by the new MediaDrm APIs to support playback of Widevine/CENC protected content. Change-Id: I6f57dd37083dfd96c402cb9dd137c7d74edc8f1c