Disable all protobuf dependent targets when enable_protobuf=0.

BUG=3045
TESTED=builds now when enable_protobuf=0 and modules_unittests still
includes ApmTest.* when enable_protobuf=1.

R=bjornv@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/9879004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5690 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed