Introduce VulkanProvider

For more consistent access to base vulkan functionality owned
elsewhere.

engine/src/flutter/vulkan/vulkan_provider.h

@@ -0,0 +1,20 @@
+// Copyright 2017 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 FLUTTER_VULKAN_VULKAN_PROVIDER_H_
+#define FLUTTER_VULKAN_VULKAN_PROVIDER_H_
+
+#include "flutter/vulkan/vulkan_handle.h"
+
+namespace vulkan {
+
+class VulkanProvider {
+ public:
+  virtual const vulkan::VulkanProcTable& vk() = 0;
+  virtual const vulkan::VulkanHandle<VkDevice>& vk_device() = 0;
+};
+
+}  // namespace vulkan
+
+#endif  // FLUTTER_VULKAN_VULKAN_PROVIDER_H_