Crash when using indexed db in second incognito window.

BUG=69294
TEST=sequetially open two incognito windows and visit pages using indexed db.

Review URL: http://codereview.chromium.org/6275001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@71476 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/in_process_webkit/browser_webkitclient_impl.cc

@@ -148,8 +148,10 @@ int BrowserWebKitClientImpl::databaseDeleteFile(
 }
 
 void BrowserWebKitClientImpl::idbShutdown() {
-  if (indexed_db_key_utility_client_.get())
+  if (indexed_db_key_utility_client_.get()) {
     indexed_db_key_utility_client_->EndUtilityProcess();
+    indexed_db_key_utility_client_ = NULL;
+  }
 }
 
 void BrowserWebKitClientImpl::createIDBKeysFromSerializedValuesAndKeyPath(