Use std::unique_ptr to pass around WebCryptoDigestor.

components/webcrypto/webcrypto_impl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_WEBCRYPTO_WEBCRYPTO_IMPL_H_
 #define COMPONENTS_WEBCRYPTO_WEBCRYPTO_IMPL_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "third_party/WebKit/public/platform/WebCrypto.h"
@@ skipping 78 matching lines @@
                  const blink::WebCryptoKey& base_key,
                  const blink::WebCryptoAlgorithm& import_algorithm,
                  const blink::WebCryptoAlgorithm& key_length_algorithm,
                  bool extractable,
                  blink::WebCryptoKeyUsageMask usages,
                  blink::WebCryptoResult result) override;
 
   // This method returns a digestor object that can be used to synchronously
   // compute a digest one chunk at a time. Thus, the consume does not need to
   // hold onto a large buffer with all the data to digest. Chunks can be given
-  // one at a time and the digest will be computed piecemeal. The allocated
-  // WebCrytpoDigestor that is returned by createDigestor must be freed by the
-  // caller.
-  blink::WebCryptoDigestor* createDigestor(
+  // one at a time and the digest will be computed piecemeal.
+  std::unique_ptr<blink::WebCryptoDigestor> createDigestor(
       blink::WebCryptoAlgorithmId algorithm_id) override;
 
   bool deserializeKeyForClone(const blink::WebCryptoKeyAlgorithm& algorithm,
                               blink::WebCryptoKeyType type,
                               bool extractable,
                               blink::WebCryptoKeyUsageMask usages,
                               const unsigned char* key_data,
                               unsigned key_data_size,
                               blink::WebCryptoKey& key) override;
 
   bool serializeKeyForClone(const blink::WebCryptoKey& key,
                             blink::WebVector<unsigned char>& key_data) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WebCryptoImpl);
 };
 
 }  // namespace webcrypto
 
 #endif  // COMPONENTS_WEBCRYPTO_WEBCRYPTO_IMPL_H_