[bindings] Make Crypto.getRandomValues use generated binding rather than using custom binding.

Source/modules/crypto/Crypto.idl

 /*
  * Copyright (C) 2011 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 17 matching lines @@
 
 [
     GarbageCollected,
     NoInterfaceObject
 ] interface Crypto {
     // Note that getRandomValues() is available even when the "Crypto"
     // runtime feature is disabled.
     //
     // This is for compatibility sake, since getRandomValues() predates the full
     // Web Crypto API spec.
-    [Custom, RaisesException] ArrayBufferView getRandomValues(ArrayBufferView array);
+    [RaisesException] ArrayBufferView getRandomValues(ArrayBufferView array);
 
     readonly attribute SubtleCrypto subtle;
 };