Fixing up Mediarecorder for MFF

For using the MediaRecorder in MFF (Mobile Filter Framework),
getMediaRecorder method in mediarecorder jni was earlier changed to
a non static method. Changed it back to a static method.

Also, added a new source type to MediaRecorder.VideoSource for recording
GRalloc buffers.

Change-Id: I031fad45c12b0ac9602d9e451d4767e95a86234d