Cleanup needed to use WindowContext for Android

src/gpu/vk/GrVkBackendContext.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "vk/GrVkBackendContext.h"
 #include "vk/GrVkExtensions.h"
 #include "vk/GrVkInterface.h"
@@ skipping 71 matching lines @@
     }
     if (extensions.hasInstanceExtension(VK_KHR_SWAPCHAIN_EXTENSION_NAME)) {
         instanceExtensionNames.push_back(VK_KHR_SWAPCHAIN_EXTENSION_NAME);
         extensionFlags |= kKHR_swapchain_GrVkExtensionFlag;
     }
 #ifdef SK_BUILD_FOR_WIN
     if (extensions.hasInstanceExtension(VK_KHR_WIN32_SURFACE_EXTENSION_NAME)) {
         instanceExtensionNames.push_back(VK_KHR_WIN32_SURFACE_EXTENSION_NAME);
         extensionFlags |= kKHR_win32_surface_GrVkExtensionFlag;
     }
-#elif SK_BUILD_FOR_ANDROID
+#elif defined(SK_BUILD_FOR_ANDROID)
     if (extensions.hasInstanceExtension(VK_KHR_ANDROID_SURFACE_EXTENSION_NAME)) {
         instanceExtensionNames.push_back(VK_KHR_ANDROID_SURFACE_EXTENSION_NAME);
         extensionFlags |= kKHR_android_surface_GrVkExtensionFlag;
     }
-#elif SK_BUILD_FOR_UNIX
+#elif defined(SK_BUILD_FOR_UNIX)
     if (extensions.hasInstanceExtension(VK_KHR_XCB_SURFACE_EXTENSION_NAME)) {
         instanceExtensionNames.push_back(VK_KHR_XCB_SURFACE_EXTENSION_NAME);
         extensionFlags |= kKHR_xcb_surface_GrVkExtensionFlag;
     }
 #endif
 
     const VkInstanceCreateInfo instance_create = {
         VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO,    // sType
         nullptr,                                   // pNext
         0,                                         // flags
@@ skipping 160 matching lines @@
     return ctx;
 }
 
 GrVkBackendContext::~GrVkBackendContext() {
     vkDeviceWaitIdle(fDevice);
     vkDestroyDevice(fDevice, nullptr);
     fDevice = VK_NULL_HANDLE;
     vkDestroyInstance(fInstance, nullptr);
     fInstance = VK_NULL_HANDLE;
 }