Add is_encrypted() in VideoDecoderConfig.

This is needed so that decoders can check if the video stream is encrypted or not and decide if it can support decrypting and/or decodeing the stream.

BUG=141784
TEST=media_unittest, encrypted media demo.

Review URL: https://chromiumcodereview.appspot.com/10910293

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@157324 0039d316-1c4b-4281-b951-d872f2087c98
13 files changed