Rename "test" ozone platform to "headless"

ui/ozone/BUILD.gn

Index: ui/ozone/BUILD.gn
diff --git a/ui/ozone/BUILD.gn b/ui/ozone/BUILD.gn
index fb13cd3ef4b01fa726c7b4e2f23bb80a3d159e9f..939563eca8851a7e357686ddd24853fc01bfdd60 100644
--- a/ui/ozone/BUILD.gn
+++ b/ui/ozone/BUILD.gn
@@ -40,6 +40,11 @@ if (ozone_platform_cast) {
   ozone_platform_deps += [ "platform/cast" ]
 }
 
+if (ozone_platform_headless) {
+  ozone_platforms += [ "headless" ]
+  ozone_platform_deps += [ "platform/headless" ]
+}
+
 platform_list_cc_file = "$target_gen_dir/platform_list.cc"
 platform_list_h_file = "$target_gen_dir/platform_list.h"
 platform_list_txt_file = "$target_gen_dir/platform_list.txt"
@@ -131,6 +136,7 @@ component("ozone") {
         "//ui/display/types",
         "//ui/display/util",
         "//ui/events",
+        "//ui/events/devices",
         "//ui/events/ozone:events_ozone",
         "//ui/gfx",
         "//ui/gfx/geometry",