IndexedDB: Rely on bindings for enum validation

Source/modules/indexeddb/IDBDatabase.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 271 matching lines @@
             scope.add(name);
     } else {
         ASSERT_NOT_REACHED();
     }
 
     if (scope.isEmpty()) {
         exceptionState.throwDOMException(InvalidAccessError, "The storeNames parameter was empty.");
         return nullptr;
     }
 
-    WebIDBTransactionMode mode = IDBTransaction::stringToMode(modeString, exceptionState);
+    WebIDBTransactionMode mode = IDBTransaction::stringToMode(modeString);
+    if (mode != WebIDBTransactionModeReadOnly && mode != WebIDBTransactionModeReadWrite) {

[jsbell, 2015/06/02 19:01:07]

Written this way instead of (mode == WebIDBTransactionVersionChange) in
anticipation of future transaction types.

+        exceptionState.throwTypeError("The mode provided ('" + modeString + "') is not one of 'readonly' or 'readwrite'.");

[jsbell, 2015/06/02 19:01:07]

And similarly, this could be changed to e.g. "You can't create 'versionchange'
transactions by hand." but leaving the existing message as-is for now.

+        return nullptr;
+    }
+
     if (exceptionState.hadException())
         return nullptr;
 
     if (m_versionChangeTransaction) {
         exceptionState.throwDOMException(InvalidStateError, "A version change transaction is running.");
         return nullptr;
     }
 
     if (m_closePending) {
         exceptionState.throwDOMException(InvalidStateError, "The database connection is closing.");
@@ skipping 145 matching lines @@
 {
     return EventTargetNames::IDBDatabase;
 }
 
 ExecutionContext* IDBDatabase::executionContext() const
 {
     return ActiveDOMObject::executionContext();
 }
 
 } // namespace blink