Set max output buffer size in Mod Mock

Merge from Widevine repo of http://go/wvgerrit/72392

This adds the ability of the reference code to set the maximum output
buffer size error discussed in the Recoverable Errors section of
http://go/wvdelta15

Bug: http://b/120572363 Add Recoverable Errors (mod mock)
Change-Id: I688caca22929e29b3548c3f7d1df5de5bd37bfa1

libwvdrmengine/oemcrypto/ref/src/oemcrypto_engine_ref.h

@@ -150,6 +150,11 @@ class CryptoEngine {
   // This is the same as the max subsample size, not the sample or frame size.
   virtual size_t max_buffer_size() { return 1024 * 100; }  // 100 KiB.
 
+  // If 0 no restriction, otherwise it's the max output buffer for DecryptCENC
+  // and CopyBuffer. This is the same as the max frame or sample size, not the
+  // subsample size.
+  virtual size_t max_output_size() { return 0; }
+
   virtual bool srm_update_supported() { return false; }
 
   virtual OEMCryptoResult current_srm_version(uint16_t* version) {