layers: Add getImageNode() helper

Add getImageNode() helper to core_validation and use it.
Also update DescriptorSet class to use the helper and kill
its image_map member.
diff --git a/layers/descriptor_sets.cpp b/layers/descriptor_sets.cpp
index e3f6e9d..9039a12 100644
--- a/layers/descriptor_sets.cpp
+++ b/layers/descriptor_sets.cpp
@@ -265,11 +265,10 @@
 
 cvdescriptorset::DescriptorSet::DescriptorSet(const VkDescriptorSet set, const DescriptorSetLayout *layout,
                                               const core_validation::layer_data *dev_data,
-                                              const std::unordered_map<VkImage, IMAGE_NODE> *image_map,
                                               const std::unordered_map<VkImage, VkSwapchainKHR> *image_to_swapchain_map,
                                               const std::unordered_map<VkSwapchainKHR, SWAPCHAIN_NODE *> *swapchain_map)
-    : some_update_(false), set_(set), p_layout_(layout), device_data_(dev_data), image_map_(image_map),
-      image_to_swapchain_map_(image_to_swapchain_map), swapchain_map_(swapchain_map) {
+    : some_update_(false), set_(set), p_layout_(layout), device_data_(dev_data), image_to_swapchain_map_(image_to_swapchain_map),
+      swapchain_map_(swapchain_map) {
     // Foreach binding, create default descriptors of given type
     for (uint32_t i = 0; i < p_layout_->GetBindingCount(); ++i) {
         auto type = p_layout_->GetTypeFromIndex(i);
@@ -584,7 +583,6 @@
 
 bool cvdescriptorset::ValidateImageUpdate(VkImageView image_view, VkImageLayout image_layout, VkDescriptorType type,
                                           const core_validation::layer_data *dev_data,
-                                          const std::unordered_map<VkImage, IMAGE_NODE> *image_map,
                                           const std::unordered_map<VkImage, VkSwapchainKHR> *image_to_swapchain_map,
                                           const std::unordered_map<VkSwapchainKHR, SWAPCHAIN_NODE *> *swapchain_map,
                                           std::string *error) {
@@ -601,10 +599,10 @@
     VkImage image = iv_data->image;
     VkFormat format = VK_FORMAT_MAX_ENUM;
     VkImageUsageFlags usage = 0;
-    auto img_pair = image_map->find(image);
-    if (img_pair != image_map->end()) {
-        format = img_pair->second.createInfo.format;
-        usage = img_pair->second.createInfo.usage;
+    auto image_node = getImageNode(dev_data, image);
+    if (image_node) {
+        format = image_node->createInfo.format;
+        usage = image_node->createInfo.usage;
     } else {
         // Also need to check the swapchains.
         auto swapchain_pair = image_to_swapchain_map->find(image);
@@ -1034,8 +1032,8 @@
             // Validate image
             auto image_view = update->pImageInfo[di].imageView;
             auto image_layout = update->pImageInfo[di].imageLayout;
-            if (!ValidateImageUpdate(image_view, image_layout, update->descriptorType, device_data_, image_map_,
-                                     image_to_swapchain_map_, swapchain_map_, error)) {
+            if (!ValidateImageUpdate(image_view, image_layout, update->descriptorType, device_data_, image_to_swapchain_map_,
+                                     swapchain_map_, error)) {
                 std::stringstream error_str;
                 error_str << "Attempted write update to combined image sampler descriptor failed due to: " << error->c_str();
                 *error = error_str.str();
@@ -1066,8 +1064,8 @@
         for (uint32_t di = 0; di < update->descriptorCount; ++di) {
             auto image_view = update->pImageInfo[di].imageView;
             auto image_layout = update->pImageInfo[di].imageLayout;
-            if (!ValidateImageUpdate(image_view, image_layout, update->descriptorType, device_data_, image_map_,
-                                     image_to_swapchain_map_, swapchain_map_, error)) {
+            if (!ValidateImageUpdate(image_view, image_layout, update->descriptorType, device_data_, image_to_swapchain_map_,
+                                     swapchain_map_, error)) {
                 std::stringstream error_str;
                 error_str << "Attempted write update to image descriptor failed due to: " << error->c_str();
                 *error = error_str.str();
@@ -1157,8 +1155,8 @@
             // Validate image
             auto image_view = img_samp_desc->GetImageView();
             auto image_layout = img_samp_desc->GetImageLayout();
-            if (!ValidateImageUpdate(image_view, image_layout, type, device_data_, image_map_, image_to_swapchain_map_,
-                                     swapchain_map_, error)) {
+            if (!ValidateImageUpdate(image_view, image_layout, type, device_data_, image_to_swapchain_map_, swapchain_map_,
+                                     error)) {
                 std::stringstream error_str;
                 error_str << "Attempted copy update to combined image sampler descriptor failed due to: " << error->c_str();
                 *error = error_str.str();
@@ -1171,8 +1169,8 @@
             auto img_desc = static_cast<const ImageDescriptor *>(src_set->descriptors_[index + di].get());
             auto image_view = img_desc->GetImageView();
             auto image_layout = img_desc->GetImageLayout();
-            if (!ValidateImageUpdate(image_view, image_layout, type, device_data_, image_map_, image_to_swapchain_map_,
-                                     swapchain_map_, error)) {
+            if (!ValidateImageUpdate(image_view, image_layout, type, device_data_, image_to_swapchain_map_, swapchain_map_,
+                                     error)) {
                 std::stringstream error_str;
                 error_str << "Attempted copy update to image descriptor failed due to: " << error->c_str();
                 *error = error_str.str();
@@ -1283,7 +1281,6 @@
     const AllocateDescriptorSetsData *ds_data, std::unordered_map<VkDescriptorPool, DESCRIPTOR_POOL_NODE *> *pool_map,
     std::unordered_map<VkDescriptorSet, cvdescriptorset::DescriptorSet *> *set_map, const core_validation::layer_data *dev_data,
     const std::unordered_map<VkDescriptorSetLayout, cvdescriptorset::DescriptorSetLayout *> &layout_map,
-    const std::unordered_map<VkImage, IMAGE_NODE> &image_map,
     const std::unordered_map<VkImage, VkSwapchainKHR> &image_to_swapchain_map,
     const std::unordered_map<VkSwapchainKHR, SWAPCHAIN_NODE *> &swapchain_map) {
     auto pool_state = (*pool_map)[p_alloc_info->descriptorPool];
@@ -1296,7 +1293,7 @@
      * global map and the pool's set.
      */
     for (uint32_t i = 0; i < p_alloc_info->descriptorSetCount; i++) {
-        auto new_ds = new cvdescriptorset::DescriptorSet(descriptor_sets[i], ds_data->layout_nodes[i], dev_data, &image_map,
+        auto new_ds = new cvdescriptorset::DescriptorSet(descriptor_sets[i], ds_data->layout_nodes[i], dev_data,
                                                          &image_to_swapchain_map, &swapchain_map);
 
         pool_state->sets.insert(new_ds);