third_party: Add secure_output_protocol target to wayland-protocols.

third_party/wayland-protocols/BUILD.gn

Index: third_party/wayland-protocols/BUILD.gn
diff --git a/third_party/wayland-protocols/BUILD.gn b/third_party/wayland-protocols/BUILD.gn
index e3156926f4a8a86ad020b682d809bcd7f8023386..35a7909bfe3ed99921a7a5755d72300f62d8bf01 100644
--- a/third_party/wayland-protocols/BUILD.gn
+++ b/third_party/wayland-protocols/BUILD.gn
@@ -64,3 +64,24 @@ source_set("scaler_protocol") {
 
   public_configs = [ ":scaler_protocol_config" ]
 }
+
+config("secure_contents_protocol_config") {
+  include_dirs = [ "include/protocol" ]
+}
+
+source_set("secure_contents_protocol") {
+  sources = [
+    "include/protocol/secure-contents-unstable-v1-client-protocol.h",
+    "include/protocol/secure-contents-unstable-v1-server-protocol.h",
+    "protocol/secure-contents-protocol.c",
+  ]
+
+  deps = [
+    "//third_party/wayland:wayland_util",
+  ]
+
+  configs -= [ "//build/config/compiler:chromium_code" ]
+  configs += [ "//build/config/compiler:no_chromium_code" ]
+
+  public_configs = [ ":secure_contents_protocol_config" ]
+}