Allow OSExchangeData::Provider to be overridden at run time.

ui/base/dragdrop/os_exchange_data_provider_factory.h

+// Copyright 2016 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.
+
+#ifndef UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_FACTORY_H_
+#define UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_FACTORY_H_
+
+#include <memory>
+
+#include "ui/base/dragdrop/os_exchange_data.h"
+#include "ui/base/ui_base_export.h"
+
+namespace ui {
+
+// Builds OSExchangeDataProviders. We need to be able to switch providers at
+// runtime based on the configuration flags. If no factory is set,
+// CreateProvider() will default to the current operating system's default.
+class UI_BASE_EXPORT OSExchangeDataProviderFactory {
+ public:
+  class Factory {
+   public:
+    virtual std::unique_ptr<OSExchangeData::Provider> BuildProvider() = 0;
+  };
+
+  // Sets the factory which builds the providers.
+  static void SetFactory(Factory* factory);
+
+  // Creates a Provider based on the current configuration.
+  static std::unique_ptr<OSExchangeData::Provider> CreateProvider();
+};
+
+}  // namespace ui
+
+#endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_FACTORY_H_