Tokens

Overview

This directory contains strongly-typed wrappers (using base::TokenType<...>) of base::UnguessableToken for tokens that are commonly passed between browsers and renderers. The strong typing is to prevent type confusion as these tokens are passed around. To support strong typing through the entire stack (including IPC) these tokens additionally include content/ and blink/ specific typemaps, as well as Mojo struct definitions.

Adding a new token

Suppose you want to add a new token type. You would do the following:

• Add a new C++ token type to /third_party/blink/public/common/tokens/tokens.h.
• Add an equivalent Mojom token type to /third_party/blink/public/mojom/tokens/tokens.mojom. Be sure to follow the convention that the struct contains a single base.mojom.UnguessableToken member named value.
• Create a new Mojom traits declaration to /third_party/blink/public/common/tokens/tokens_mojom_traits.h. Use the templated TokenMojomTraitsHelper<...> helper class.
• Update mojom/tokens/BUILD.gn and add a new typemap definition for the token to the shared_cpp_typemaps section.
• If your token needs to be sent via legacy IPC as well, add the appropriate definition to /content/common/content_param_traits.h.