Replace some nullptrs with VK_NULL_HANDLE

src/gpu/vk/GrVkProgram.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 "GrVkProgram.h"
 
 #include "GrPipeline.h"
@@ skipping 82 matching lines @@
         fPipeline = nullptr;
     }
     if (fDescriptorPool) {
         fDescriptorPool->unref(gpu);
         fDescriptorPool = nullptr;
     }
     if (fPipelineLayout) {
         GR_VK_CALL(gpu->vkInterface(), DestroyPipelineLayout(gpu->device(),
                                                              fPipelineLayout,
                                                              nullptr));
-        fPipelineLayout = nullptr;
+        fPipelineLayout = VK_NULL_HANDLE;
     }
 
     if (fDSLayout[0]) {
         GR_VK_CALL(gpu->vkInterface(), DestroyDescriptorSetLayout(gpu->device(), fDSLayout[0],
                                                                   nullptr));
-        fDSLayout[0] = nullptr;
+        fDSLayout[0] = VK_NULL_HANDLE;
     }
     if (fDSLayout[1]) {
         GR_VK_CALL(gpu->vkInterface(), DestroyDescriptorSetLayout(gpu->device(), fDSLayout[1],
                                                                   nullptr));
-        fDSLayout[1] = nullptr;
+        fDSLayout[1] = VK_NULL_HANDLE;
     }
 
     if (fVertexUniformBuffer) {
         fVertexUniformBuffer->release(gpu);
     }
 
     if (fFragmentUniformBuffer) {
         fFragmentUniformBuffer->release(gpu);
     }
     this->freeTempResources(gpu);
 }
 
 void GrVkProgram::abandonGPUResources() {
     fPipeline->unrefAndAbandon();
     fPipeline = nullptr;
     fDescriptorPool->unrefAndAbandon();
     fDescriptorPool = nullptr;
-    fPipelineLayout = nullptr;
-    fDSLayout[0] = nullptr;
-    fDSLayout[1] = nullptr;
+    fPipelineLayout = VK_NULL_HANDLE;
+    fDSLayout[0] = VK_NULL_HANDLE;
+    fDSLayout[1] = VK_NULL_HANDLE;
 
     fVertexUniformBuffer->abandon();
     fFragmentUniformBuffer->abandon();
 
     for (int i = 0; i < fSamplers.count(); ++i) {
         fSamplers[i]->unrefAndAbandon();
     }
     fSamplers.rewind();
 
     for (int i = 0; i < fTextureViews.count(); ++i) {
@@ skipping 213 matching lines @@
 
     for (int i = 0; i < fTextureViews.count(); ++i) {
         commandBuffer.addResource(fTextureViews[i]);
     }
 
     for (int i = 0; i < fTextures.count(); ++i) {
         commandBuffer.addResource(fTextures[i]);
     }
 #endif
 }