Move non-gfx things out of `gfx_traits` and create a `base` crate (#32296)

For a long time, `gfx_traits` has held a lot of things unrelated to graphics
and also unrelated to the `gfx` crate (which is mostly about fonts).
This is a cleanup which does a few things:

1. Move non `gfx` crate things out of `gfx_traits`. This is important in
   order to prevent dependency cycles with a different integration between
   layout, script, and fonts.
2. Rename the `msg` crate to `base`. It didn't really contain anything
   to do with messages and instead mostly holds ids, which are used
   across many different crates in Servo. This new crate will hold the
   *rare* data types that are widely used.

Details:

 - All BackgroundHangMonitor-related things from base to a new
   `background_hang_monitor_api` crate.
 - Moved `TraversalDirection` to `script_traits`
 - Moved `Epoch`-related things from `gfx_traits` to `base`.
 - Moved `PrintTree` to base. This should be widely useful in Servo.
 - Moved `WebrenderApi` from `base` to `webrender_traits` and renamed it
   to `WebRenderFontApi`.

1 files changed, 4 insertions, 4 deletions

diff --git a/ports/jniapi/src/simpleservo.rs b/ports/jniapi/src/simpleservo.rs
index d13fb2668ab..cf9a65bbe02 100644
--- a/ports/jniapi/src/simpleservo.rs
+++ b/ports/jniapi/src/simpleservo.rs
@@ -12,6 +12,7 @@ use std::rc::Rc;
 use getopts::Options;
 use ipc_channel::ipc::IpcSender;
 use log::{debug, info, warn};
+use servo::base::id::WebViewId;
 use servo::compositing::windowing::{
     AnimationState, EmbedderCoordinates, EmbedderEvent, EmbedderMethods, MouseWindowEvent,
     WindowMethods,
@@ -21,18 +22,17 @@ use servo::config::prefs::pref_map;
 pub use servo::config::prefs::{add_user_prefs, PrefValue};
 use servo::embedder_traits::resources::{self, Resource, ResourceReaderMethods};
 pub use servo::embedder_traits::{
-    ContextMenuResult, MediaSessionPlaybackState, PermissionPrompt, PermissionRequest, PromptResult,
+    ContextMenuResult, InputMethodType, MediaSessionPlaybackState, PermissionPrompt,
+    PermissionRequest, PromptResult,
 };
 use servo::embedder_traits::{
     EmbedderMsg, EmbedderProxy, MediaSessionEvent, PromptDefinition, PromptOrigin,
 };
 use servo::euclid::{Point2D, Rect, Scale, Size2D, Vector2D};
 use servo::keyboard_types::{Key, KeyState, KeyboardEvent};
-pub use servo::msg::constellation_msg::InputMethodType;
-use servo::msg::constellation_msg::{TraversalDirection, WebViewId};
 use servo::rendering_context::RenderingContext;
 pub use servo::script_traits::{MediaSessionActionType, MouseButton};
-use servo::script_traits::{TouchEventType, TouchId};
+use servo::script_traits::{TouchEventType, TouchId, TraversalDirection};
 use servo::servo_config::{opts, pref};
 use servo::servo_url::ServoUrl;
 pub use servo::webrender_api::units::DeviceIntRect;