Add HDR Metadata extension

Basic framework to support HDR Metadata extension. Will
add system plumbing in separate CL.

Test: CTS dEQP-VK.wsi.android.hdr_metadata.scale_none.fifo.*
Change-Id: I5de639ef87a988e02d194a2bd91d16ffe6102c6e
diff --git a/vulkan/libvulkan/driver_gen.h b/vulkan/libvulkan/driver_gen.h
index 95c70f8..273e796 100644
--- a/vulkan/libvulkan/driver_gen.h
+++ b/vulkan/libvulkan/driver_gen.h
@@ -35,11 +35,12 @@
     enum Extension {
         ANDROID_native_buffer,
         EXT_debug_report,
+        EXT_hdr_metadata,
+        GOOGLE_display_timing,
         KHR_android_surface,
         KHR_incremental_present,
         KHR_surface,
         KHR_swapchain,
-        GOOGLE_display_timing,
         KHR_shared_presentable_image,
 
         EXTENSION_CORE,  // valid bit