Implement OpenGL backend in Android viewer app

tools/viewer/sk_app/android/VulkanWindowContext_android.cpp

 
 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#include "VulkanWindowContext_android.h"
+#include "Window_android.h"
+#include "../VulkanWindowContext.h"
 
 #include "vk/GrVkInterface.h"
 #include "vk/GrVkUtil.h"
 
 namespace sk_app {
 
 VkSurfaceKHR VulkanWindowContext::createVkSurface(VkInstance instance, void* platformData) {
     static PFN_vkCreateAndroidSurfaceKHR createAndroidSurfaceKHR = nullptr;
     if (!createAndroidSurfaceKHR) {
         createAndroidSurfaceKHR = (PFN_vkCreateAndroidSurfaceKHR)vkGetInstanceProcAddr(instance,
@@ skipping 18 matching lines @@
                                            nullptr, &surface);
     return (VK_SUCCESS == res) ? surface : VK_NULL_HANDLE;
 }
 
 bool VulkanWindowContext::canPresent(VkInstance instance, VkPhysicalDevice physDev,
                                      uint32_t queueFamilyIndex, void*) {
     return true;
 }
 
 }   // namespace sk_app