Layered Clock interface

Merge from Widevine repo of http://go/wvgerrit/131306
which is a
Merge of non OPK files from http://go/wvgerrit/129344
and http://go/wvgerrit/129563. The OPK files are squash merged
in the CL http://go/wvgerrit/131303.

This splits the clock interface into two layers so that we can save
the previous value.

Bug: 158719238
Change-Id: I473966eb9b0766d27372682e8ebfbcb53f546980

libwvdrmengine/cdm/core/test/test_printers.cpp

@@ -1220,6 +1220,9 @@ void PrintTo(const enum OEMCryptoResult& value, ::std::ostream* os) {
     case OPK_ERROR_REMOTE_CALL:
       *os << "REMOTE_CALL";
       break;
+    case OPK_ERROR_NO_PERSISTENT_DATA:
+      *os << "NO_PERSISTENT_DATA";
+      break;
   }
 }
 namespace okp {