Add support for v0.3 of the encrypted WebM specification.

media/base/decrypt_config.h

Index: media/base/decrypt_config.h
diff --git a/media/base/decrypt_config.h b/media/base/decrypt_config.h
index d8ad224c51ca58e56d8df5886b1949538494ead5..669aa36bb1684ab04f6bfa74d332aa7800a08f85 100644
--- a/media/base/decrypt_config.h
+++ b/media/base/decrypt_config.h
@@ -36,7 +36,9 @@ class MEDIA_EXPORT DecryptConfig {
 
   // |key_id| is the ID that references the decryption key for this sample.
   // |iv| is the initialization vector defined by the encrypted format.
-  //   Currently |iv_size| must be 16 bytes as defined by WebM and ISO.
+  //   Currently |iv| must be 16 bytes as defined by WebM and ISO. Or must be
+  //   empty which signals to perform the integrity check on an unencrypted
+  //   frame as defined WebM.
   // |checksum| is the hash value of the encrypted buffer. |checksum| is
   //   defined by the encrypted format and may be NULL.
   // |data_offset| is the amount of data that should be discarded from the