layers: export debug_report extension

Need the EnumerateInstanceExtensionProperties to report
support for the debug report extension as well as in
the json file because different platforms will use either
the json file (Windows & Linux) or the Enumerate call (Android).
diff --git a/layers/mem_tracker.cpp b/layers/mem_tracker.cpp
index 62a78ba..c77f1cd 100644
--- a/layers/mem_tracker.cpp
+++ b/layers/mem_tracker.cpp
@@ -1180,12 +1180,10 @@
     memcpy(&memProps, pMemoryProperties, sizeof(VkPhysicalDeviceMemoryProperties));
 }
 
-static const VkLayerProperties mtGlobalLayers[] = {
+static const VkExtensionProperties instance_extensions[] = {
     {
-        "MemTracker",
-        VK_API_VERSION,
-        VK_MAKE_VERSION(0, 1, 0),
-        "Validation layer: MemTracker",
+        VK_EXT_LUNARG_DEBUG_REPORT_EXTENSION_NAME,
+        VK_EXT_LUNARG_DEBUG_REPORT_EXTENSION_REVISION
     }
 };
 
@@ -1194,10 +1192,18 @@
         uint32_t              *pCount,
         VkExtensionProperties *pProperties)
 {
-    /* Mem tracker does not have any global extensions */
-    return util_GetExtensionProperties(0, NULL, pCount, pProperties);
+    return util_GetExtensionProperties(1, instance_extensions, pCount, pProperties);
 }
 
+static const VkLayerProperties mtGlobalLayers[] = {
+    {
+        "MemTracker",
+        VK_API_VERSION,
+        VK_MAKE_VERSION(0, 1, 0),
+        "Validation layer: MemTracker",
+    }
+};
+
 VK_LAYER_EXPORT VKAPI_ATTR VkResult VKAPI_CALL vkEnumerateInstanceLayerProperties(
         uint32_t          *pCount,
         VkLayerProperties *pProperties)