[webcrypto] Interpret empty BigInteger as 0 according to the spec

Source/modules/crypto/NormalizeAlgorithm.cpp

 /*
  * 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 299 matching lines @@
 
 // Defined by the WebCrypto spec as:
 //
 //     typedef Uint8Array BigInteger;
 bool getBigInteger(const Dictionary& raw, const char* propertyName, RefPtr<Uint8Array>& array, const ErrorContext& context, AlgorithmError* error)
 {
     if (!getUint8Array(raw, propertyName, array, context, error))
         return false;
 
     if (!array->byteLength()) {
-        setSyntaxError(context.toString(propertyName, "BigInteger should not be empty"), error);
-        return false;
+        // Empty BigIntegers represent 0 according to the spec
+        array = Uint8Array::create(1);
     }
 
-    if (!DictionaryHelper::get(raw, propertyName, array) || !array) {
-        setSyntaxError(context.toString(propertyName, "Missing or not a Uint8Array"), error);
-        return false;
-    }
     return true;
 }
 
 // Gets an integer according to WebIDL's [EnforceRange].
 bool getOptionalInteger(const Dictionary& raw, const char* propertyName, bool& hasProperty, double& value, double minValue, double maxValue, const ErrorContext& context, AlgorithmError* error)
 {
     double number;
     bool ok = DictionaryHelper::get(raw, propertyName, number, hasProperty);
 
     if (!hasProperty)
@@ skipping 400 matching lines @@
 }
 
 } // namespace
 
 bool normalizeAlgorithm(const Dictionary& raw, WebCryptoOperation op, WebCryptoAlgorithm& algorithm, AlgorithmError* error)
 {
     return parseAlgorithm(raw, op, algorithm, ErrorContext(), error);
 }
 
 } // namespace blink