Vulkan: Add comment for Android validation layers.

Note: these also require minor tweaks to Local.mk to include, currently,
but we're probably moving to gradle.

Common/Vulkan/VulkanContext.cpp

@@ -37,6 +37,16 @@ static const char *validationLayers[] = {
 	"VK_LAYER_LUNARG_object_tracker",
 	"VK_LAYER_LUNARG_param_checker",
 	*/
+	/*
+	// For layers included in the Android NDK.
+	"VK_LAYER_GOOGLE_threading",
+	"VK_LAYER_LUNARG_parameter_validation",
+	"VK_LAYER_LUNARG_core_validation",
+	"VK_LAYER_LUNARG_image",
+	"VK_LAYER_LUNARG_object_tracker",
+	"VK_LAYER_LUNARG_swapchain",
+	"VK_LAYER_GOOGLE_unique_objects",
+	*/
 };
 
 static VkBool32 CheckLayers(const std::vector<layer_properties> &layer_props, const std::vector<const char *> &layer_names);