Setup system in Vulkan to reuse VkDescriptorSet allocations.

src/gpu/vk/GrVkDescriptorSet.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 "GrVkDescriptorSet.h"
+
+#include "GrVkDescriptorPool.h"
+#include "GrVkGpu.h"
+#include "GrVkResourceProvider.h"
+
+GrVkDescriptorSet::GrVkDescriptorSet(VkDescriptorSet descSet,
+                                     GrVkDescriptorPool* pool,
+                                     GrVkDescriptorSetManager::Handle handle)
+    : fDescSet(descSet)
+    , fPool(pool)
+    , fHandle(handle) {
+    fPool->ref();
+}
+
+void GrVkDescriptorSet::freeGPUData(const GrVkGpu* gpu) const {
+    fPool->unref(gpu);
+}
+
+void GrVkDescriptorSet::onRecycle(GrVkGpu* gpu) const {
+    gpu->resourceProvider().recycleDescriptorSet(this, fHandle);
+}
+
+void GrVkDescriptorSet::abandonSubResources() const {
+    fPool->unrefAndAbandon();
+}
+