layers: Add white-list helper to layer utils

Change-Id: Idfc67481589ea9698ab82501889680044fcf8276
diff --git a/layers/vk_layer_utils.cpp b/layers/vk_layer_utils.cpp
index 48b3f6e..412a5a3 100644
--- a/layers/vk_layer_utils.cpp
+++ b/layers/vk_layer_utils.cpp
@@ -629,6 +629,13 @@
     return result;
 }
 
+// Utility function for finding a text string in another string
+bool white_list(const char *item, const char *list) {
+    std::string candidate(item);
+    std::string white_list(list);
+    return (white_list.find(candidate) != std::string::npos);
+}
+
 // Debug callbacks get created in three ways:
 //   o  Application-defined debug callbacks
 //   o  Through settings in a vk_layer_settings.txt file
diff --git a/layers/vk_layer_utils.h b/layers/vk_layer_utils.h
index 7db58fc..623f0c5 100644
--- a/layers/vk_layer_utils.h
+++ b/layers/vk_layer_utils.h
@@ -116,6 +116,7 @@
 VkFormatCompatibilityClass vk_format_get_compatibility_class(VkFormat format);
 VkDeviceSize vk_safe_modulo(VkDeviceSize dividend, VkDeviceSize divisor);
 VkStringErrorFlags vk_string_validate(const int max_length, const char *char_array);
+bool white_list(const char *item, const char *whitelist);
 
 static inline int u_ffs(int val) {
 #ifdef WIN32