Add binding function to create empty DeclarationBlock

components/style/gecko_bindings/bindings.rs

@@ -922,6 +922,10 @@ extern "C" {
     pub fn Servo_ParseStyleAttribute(data: *const nsACString_internal)
      -> RawServoDeclarationBlockStrong;
 }
+extern "C" {
+    pub fn Servo_DeclarationBlock_CreateEmpty()
+     -> RawServoDeclarationBlockStrong;
+}
 extern "C" {
     pub fn Servo_DeclarationBlock_Equals(a: RawServoDeclarationBlockBorrowed,
                                          b: RawServoDeclarationBlockBorrowed)