Improve Crypto::getRandomValues exception messages.

Source/modules/crypto/Crypto.cpp

 /*
  * 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 43 matching lines @@
 }
 
 Crypto::Crypto()
 {
     ScriptWrappable::init(this);
 }
 
 // Note: This implementation must be thread-safe, as it is used by workers.
 void Crypto::getRandomValues(ArrayBufferView* array, ExceptionState& exceptionState)
 {
-    if (!array || !isIntegerArray(array)) {
-        exceptionState.throwUninformativeAndGenericDOMException(TypeMismatchError);
+    if (!array) {
+        exceptionState.throwDOMException(TypeMismatchError, "The provided ArrayBufferView is null.");
+        return;
+    }
+    if (!isIntegerArray(array)) {
+        exceptionState.throwDOMException(TypeMismatchError, String::format("The provided ArrayBufferView is of type '%s', which is not an integer array type.", array->typeName()));
         return;
     }
     if (array->byteLength() > 65536) {
-        exceptionState.throwUninformativeAndGenericDOMException(QuotaExceededError);
+        exceptionState.throwDOMException(QuotaExceededError, String::format("The ArrayBufferView's byte length (%u) exceeds the number of bytes of entropy available via this API (65536).", array->byteLength()));
         return;
     }
     cryptographicallyRandomValues(array->baseAddress(), array->byteLength());
 }
 
 SubtleCrypto* Crypto::subtle()
 {
     if (!m_subtleCrypto)
         m_subtleCrypto = SubtleCrypto::create();
     return m_subtleCrypto.get();
 }
 
 }