Improve modules' TypeError exception messages.

Source/modules/indexeddb/IDBCursor.cpp

 /*
  * Copyright (C) 2010 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 143 matching lines @@
     if (m_transaction->isFinished()) {
         exceptionState.throwDOMException(TransactionInactiveError, IDBDatabase::transactionFinishedErrorMessage);
         return;
     }
     if (!m_transaction->isActive()) {
         exceptionState.throwDOMException(TransactionInactiveError, IDBDatabase::transactionInactiveErrorMessage);
         return;
     }
 
     if (!count) {
-        exceptionState.throwUninformativeAndGenericTypeError();
+        exceptionState.throwTypeError("The count provided is 0.");
         return;
     }
 
     m_request->setPendingCursor(this);
     m_gotValue = false;
     m_backend->advance(count, WebIDBCallbacksImpl::create(m_request).leakPtr());
 }
 
 void IDBCursor::continueFunction(ExecutionContext* context, const ScriptValue& keyValue, ExceptionState& exceptionState)
 {
@@ skipping 210 matching lines @@
 {
     if (directionString.isNull() || directionString == IDBCursor::directionNext())
         return IndexedDB::CursorNext;
     if (directionString == IDBCursor::directionNextUnique())
         return IndexedDB::CursorNextNoDuplicate;
     if (directionString == IDBCursor::directionPrev())
         return IndexedDB::CursorPrev;
     if (directionString == IDBCursor::directionPrevUnique())
         return IndexedDB::CursorPrevNoDuplicate;
 
-    exceptionState.throwUninformativeAndGenericTypeError();
+    exceptionState.throwTypeError("The direction provided ('" + directionString + "') is not one of 'next', 'nextunique', 'prev', or 'prevunique'.");
     return IndexedDB::CursorNext;
 }
 
 const AtomicString& IDBCursor::directionToString(unsigned short direction)
 {
     switch (direction) {
     case IndexedDB::CursorNext:
         return IDBCursor::directionNext();
 
     case IndexedDB::CursorNextNoDuplicate:
         return IDBCursor::directionNextUnique();
 
     case IndexedDB::CursorPrev:
         return IDBCursor::directionPrev();
 
     case IndexedDB::CursorPrevNoDuplicate:
         return IDBCursor::directionPrevUnique();
 
     default:
         ASSERT_NOT_REACHED();
         return IDBCursor::directionNext();
     }
 }
 
 } // namespace WebCore