Modifiable OEMCrypto

Merge from Widevine repo of http://go/wvgerrit/24729

This CL adds a new variant of the OEMCrypto mock code that adjusts its
behaviour based on a configuration file.  This is intended for
testing.

For example, a tester can set current_hdcp to 2 in the options.txt
file, push it to the device, and verify that a license is granted for
HDCP 2.0.  Then the tester can edit the value of current_hdcp to 1 and
push the file to the device.  Playback should stop because the license
is no longer valid.

This variant uses a real level 1 liboemcrypto.so to push data to a
secure buffer.  That means we can test playback for a license that
requires secure buffers on an Android device with real secure buffers.

b/35141278
b/37353534

Change-Id: Id12f2800c6395d9da7cffebd6797aac17414b38d

libwvdrmengine/oemcrypto/mock/src/oemcrypto_engine_mock.cpp

@@ -112,6 +112,7 @@ OEMCryptoResult CryptoEngine::SetDestination(
     LOGE("[SetDestination(): OEMCrypto_ERROR_SHORT_BUFFER]");
     return OEMCrypto_ERROR_SHORT_BUFFER;
   }
+  adjust_destination(out_description, data_length, subsample_flags);
   if ((out_description->type != OEMCrypto_BufferType_Direct) &&
       (destination_ == NULL)) {
     return OEMCrypto_ERROR_INVALID_CONTEXT;