Support Latest Version of EME Spec Init Data Specification

(This is a merge of
https://widevine-internal-review.googlesource.com/9711 from the
Widevine CDM repo.)

This change updates the CDM's handling of init data types, previously
known as MIME types, to comply with the latest version of the EME
spec.

Following this change, in addition to accepting the deprecated MIME
types "video/mp4", "audio/mp4", "video/webm", and "audio/webm", the
CDM will accept the new standard: Init data types "cenc" and "webm".

Furthermore, this removes the non-PSSH-parsing path from the CDM. All
platforms have unified on the CDM being responsible for parsing the
concatenated PSSH box list, as outlined in the latest EME spec.

As Android has shipped code that expects pre-unwrapped PSSH boxes and
must maintain backwards-compatibility, code has been inserted on that
platform to detect pre-unwrapped data and re-wrap it with a PSSH
header before sending it to the CDM.

There are some small changes to unit tests because of this change:

1) The CDM Engine unit test now no longer needs to unwrap the PSSH on
   any platforms when testing ISO-BMFF. It now pre-caches the
   unwrapped key ID for use when testing WebM.

2) Several substantially-similar unit tests in the Android code have
   been rolled into one test.

Bug: 13564917
Bug: 13570595
Bug: 9465346
Bug: 13570288
Change-Id: I7f27b16b8503f24a26746b5dce71fb61b6fd1bb2

libwvdrmengine/cdm/include/wv_content_decryption_module.h

@@ -21,7 +21,9 @@ class WvContentDecryptionModule : public TimerHandler {
   virtual ~WvContentDecryptionModule();
 
   // Static methods
-  static bool SupportsInitDataType(const std::string& type);
+  static bool IsSupported(const std::string& init_data_type);
+  static bool IsCenc(const std::string& init_data_type);
+  static bool IsWebm(const std::string& init_data_type);
 
   // Session related methods
   virtual CdmResponseType OpenSession(