Google did it again, and there's a kind of hype around this new wheel.
Protocol Buffers are a bit simplified form of ASN.1 notation, which has been in use for decades. They even mention BER (Basic Encoding Rules, a form of ASN.1) but hide the "ASN" name.
This is what happens when imported eastern developers are writers and not readers.
Sometimes I feel pity that standards and protocols are not patented. One should prosecute those "reinventors" for plagiarism (taking the industry-adopted standard, hiding its name and claiming it the new protocol or something).