Implement "Key Presence" step in "Encrypted Block Encounted" algorithm in EME.

media/crypto/aes_decryptor_unittest.cc

Index: media/crypto/aes_decryptor_unittest.cc
diff --git a/media/crypto/aes_decryptor_unittest.cc b/media/crypto/aes_decryptor_unittest.cc
index ab314de71275a0089e5a7c8fb0425c01599d0106..c9d82c2e62d0d1ad93f47037e40bfd50b0e9e1fe 100644
--- a/media/crypto/aes_decryptor_unittest.cc
+++ b/media/crypto/aes_decryptor_unittest.cc
@@ -346,6 +346,17 @@ TEST_F(AesDecryptorTest, WrongKey) {
   ASSERT_NO_FATAL_FAILURE(DecryptAndExpectToFail(encrypted_data));
 }
 
+TEST_F(AesDecryptorTest, NoKey) {
+  const WebmEncryptedData& frame = kWebmEncryptedFrames[0];
+  GenerateKeyRequest(frame.key_id, frame.key_id_size);
+
+  scoped_refptr<DecoderBuffer> encrypted_data =
+      CreateWebMEncryptedBuffer(frame.encrypted_data, frame.encrypted_data_size,
+                                frame.key_id, frame.key_id_size);
+  EXPECT_CALL(*this, BufferDecrypted(AesDecryptor::kNoKey, IsNull()));
+  decryptor_.Decrypt(encrypted_data, decrypt_cb_);
+}
+
 TEST_F(AesDecryptorTest, KeyReplacement) {
   const WebmEncryptedData& frame = kWebmEncryptedFrames[0];
   GenerateKeyRequest(frame.key_id, frame.key_id_size);