DEFINE_EMPTY_PROTOCOL   28 base/mac/cocoa_protocols.h DEFINE_EMPTY_PROTOCOL(NSDraggingDestination)
DEFINE_EMPTY_PROTOCOL   29 base/mac/cocoa_protocols.h DEFINE_EMPTY_PROTOCOL(ICCameraDeviceDownloadDelegate)
DEFINE_EMPTY_PROTOCOL   33 base/mac/cocoa_protocols.h #undef DEFINE_EMPTY_PROTOCOL