Create a `constellation_traits` crate (#36088)

This change creates a `constellation_traits` crate. Previously messages
to the `Constellation` were in the `compositing_traits` crate, which
came about organically. This change moves these to a new crate which
also contains data types that are used in both compositing/libservo and
script (ie types that cross the process boundary). The idea is similar
to `embedding_traits`, but this is meant for types not exposed to the
API.

This change allows deduplicating `UntrustedNodeAddress`, which
previously had two versions to avoid circular dependencies.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

1 files changed, 6 insertions, 9 deletions

diff --git a/components/shared/embedder/lib.rs b/components/shared/embedder/lib.rs
index a0ec13b2f1e..d2183730df2 100644
--- a/components/shared/embedder/lib.rs
+++ b/components/shared/embedder/lib.rs
@@ -2,6 +2,12 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+//! Types used by the embedding layer and/or exposed to the API. This crate is responsible for
+//! defining types that cross the process boundary from the embedding/rendering layer all the way
+//! to script, thus it should have very minimal dependencies on other parts of Servo. If a type
+//! is not exposed in the API or doesn't involve messages sent to the embedding/libservo layer, it
+//! is probably a better fit for the `constellation_traits` crate.
+
 pub mod input_events;
 pub mod resources;
 mod webdriver;
@@ -526,15 +532,6 @@ impl WebResourceResponse {
     }
 }
 
-/// The direction of a history traversal
-#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
-pub enum TraversalDirection {
-    /// Travel forward the given number of documents.
-    Forward(usize),
-    /// Travel backward the given number of documents.
-    Back(usize),
-}
-
 /// The type of platform theme.
 #[derive(Clone, Copy, Debug, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
 pub enum Theme {