Add OpenGL support to Linux viewer

tools/viewer/sk_app/VulkanWindowContext.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 "GrContext.h"
 #include "GrRenderTarget.h"
@@ skipping 370 matching lines @@
 
 VulkanWindowContext::~VulkanWindowContext() {
     this->destroyContext();
 }
 
 void VulkanWindowContext::destroyContext() {
     if (!fBackendContext.get()) {
         return;
     }
 
+    GR_VK_CALL(fBackendContext->fInterface, QueueWaitIdle(fPresentQueue));
     GR_VK_CALL(fBackendContext->fInterface, DeviceWaitIdle(fBackendContext->fDevice));
 
     this->destroyBuffers();
 
     if (VK_NULL_HANDLE != fCommandPool) {
         GR_VK_CALL(fBackendContext->fInterface, DestroyCommandPool(fBackendContext->fDevice,
                                                                    fCommandPool, nullptr));
         fCommandPool = VK_NULL_HANDLE;
     }
 
@@ skipping 193 matching lines @@
         &fSwapchain, // pSwapchains
         &backbuffer->fImageIndex, // pImageIndices
         NULL // pResults
     };
 
     fQueuePresentKHR(fPresentQueue, &presentInfo);
 
 }
 
 }   //namespace sk_app