Fix media_cas_proxy_sdk build issue.

Add example binary for testing building the SDK after 'git clone' from our repo.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=227583629

common/crypto_util.cc

@@ -22,8 +22,8 @@
 namespace widevine {
 namespace crypto_util {
 
-const char kEncryptionKeyLabel[] = "ENCRYPTION";
-const int kEncryptionKeySizeBits = 128;
+const char kWrappingKeyLabel[] = "ENCRYPTION";
+const int kWrappingKeySizeBits = 128;
 const char kSigningKeyLabel[] = "AUTHENTICATION";
 const int kSigningKeySizeBits = 256;
 const size_t kSigningKeySizeBytes = 32;