The information is generated by Edwin's copyright.py script with some
minor manual modifications.
Chromium's original copyright notice is not replaced.
Also add LICENSE file taken from
https://sites.google.com/a/google.com/ospo/releasing#TOC-BSD-License
Change-Id: I231f09af96a0a611b1ca81e95cab82e12d7f529b
Defines an abstract request signer class and two implementations of the
signer class, AesRequestSigner for AES-CBC signing and RsaRequestSigner
for RSA-PSS signing.
WidevineEncryptorSource now uses Signer for signature generation.
Change-Id: I4528409a9be998535bccde40fdadb412e4bbdaf3
Kongqun Yang