[webcrypto] Match the error handling defined by the spec.

Source/modules/crypto/NormalizeAlgorithm.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef NormalizeAlgorithm_h
 #define NormalizeAlgorithm_h
 
 #include "public/platform/WebCryptoAlgorithm.h"
 #include "wtf/Assertions.h"
+#include "wtf/Forward.h"
 
 namespace blink { class WebCryptoAlgorithm; }
 
 namespace WebCore {
 
 class Dictionary;
 class ExceptionState;
 
 enum AlgorithmOperation {
     Encrypt,
     Decrypt,
     Sign,
     Verify,
     Digest,
     GenerateKey,
     ImportKey,
     DeriveKey,
     WrapKey,
     UnwrapKey,
     // <---- End of list (keep this up-to-date)
     LastAlgorithmOperation = UnwrapKey,
 };
 
-// Normalizes an algorithm identifier (dictionary) into a WebCryptoAlgorithm. If
-// normalization fails then returns false and sets the ExceptionState.
-bool normalizeAlgorithm(const Dictionary&, AlgorithmOperation, blink::WebCryptoAlgorithm&, ExceptionState&) WARN_UNUSED_RETURN;
+// Converts a javascript Dictionary to a WebCryptoAlgorithm object.
+//
+// This corresponds with "normalizing" [1] the algorithm, and then validating
+// the expected parameters for the algorithm/operation combination.
+//
+// On success returns true and sets the WebCryptoAlgorithm.
+//
+// On failure parseAlgorithm returns false. errorDetails will be filled
+// with a (non-localized) debug string. Additionally the ExceptionState *may*
+// be set (the web crypto spec only defines a handeful of errors as resulting
+// in exceptions).
+//
+// [1] http://www.w3.org/TR/WebCryptoAPI/#algorithm-normalizing-rules
+bool parseAlgorithm(const Dictionary&, AlgorithmOperation, blink::WebCryptoAlgorithm&, String& errorDetails, ExceptionState&) WARN_UNUSED_RETURN;
 
 // Returns a null-terminated C-string literal. Caller can assume the pointer
 // will be valid for the program's entire runtime.
 const char* algorithmIdToName(blink::WebCryptoAlgorithmId);
 
 } // namespace WebCore
 
 #endif