Don't derive from ChromeURLDataManager::DataSource, and instead have these classes implement a dele…

content/public/browser/url_data_source_delegate.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/public/browser/url_data_source_delegate.h"
+
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+
+URLDataSourceDelegate::URLDataSourceDelegate()
+    : url_data_source_(NULL) {
+}
+
+URLDataSourceDelegate::~URLDataSourceDelegate() {
+}
+
+MessageLoop* URLDataSourceDelegate::MessageLoopForRequestPath(
+    const std::string& path) const {
+  return BrowserThread::UnsafeGetMessageLoopForThread(BrowserThread::UI);
+}
+
+bool URLDataSourceDelegate::ShouldReplaceExistingSource() const {
+  return true;
+}
+
+bool URLDataSourceDelegate::AllowCaching() const {
+  return true;
+}
+
+}  // namespace content