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`.

8 files changed, 27 insertions, 26 deletions

diff --git a/components/constellation/Cargo.toml b/components/constellation/Cargo.toml
index 0f10a5a23fb..851d207dfc2 100644
--- a/components/constellation/Cargo.toml
+++ b/components/constellation/Cargo.toml
@@ -15,8 +15,10 @@ default = []
 multiview = []
 
 [dependencies]
+background_hang_monitor_api = { workspace = true }
 background_hang_monitor = { path = "../background_hang_monitor" }
 backtrace = { workspace = true }
+base = { workspace = true }
 bluetooth_traits = { workspace = true }
 canvas_traits = { workspace = true }
 compositing_traits = { workspace = true }
@@ -32,7 +34,6 @@ keyboard-types = { workspace = true }
 log = { workspace = true }
 media = { path = "../media" }
 metrics = { path = "../metrics" }
-msg = { workspace = true }
 net = { path = "../net" }
 net_traits = { workspace = true }
 parking_lot = { workspace = true }
diff --git a/components/constellation/browsingcontext.rs b/components/constellation/browsingcontext.rs
index dbb956ad6c5..4f55c0fe3ac 100644
--- a/components/constellation/browsingcontext.rs
+++ b/components/constellation/browsingcontext.rs
@@ -4,11 +4,9 @@
 
 use std::collections::{HashMap, HashSet};
 
+use base::id::{BrowsingContextGroupId, BrowsingContextId, PipelineId, TopLevelBrowsingContextId};
 use euclid::Size2D;
 use log::warn;
-use msg::constellation_msg::{
-    BrowsingContextGroupId, BrowsingContextId, PipelineId, TopLevelBrowsingContextId,
-};
 use style_traits::CSSPixel;
 
 use crate::pipeline::Pipeline;
diff --git a/components/constellation/constellation.rs b/components/constellation/constellation.rs
index 53b0ae8d412..14176fc0739 100644
--- a/components/constellation/constellation.rs
+++ b/components/constellation/constellation.rs
@@ -94,6 +94,15 @@ use std::sync::{Arc, Mutex};
 use std::{process, thread};
 
 use background_hang_monitor::HangMonitorRegister;
+use background_hang_monitor_api::{
+    BackgroundHangMonitorControlMsg, BackgroundHangMonitorRegister, HangMonitorAlert,
+};
+use base::id::{
+    BroadcastChannelRouterId, BrowsingContextGroupId, BrowsingContextId, HistoryStateId,
+    MessagePortId, MessagePortRouterId, PipelineId, PipelineNamespace, PipelineNamespaceId,
+    PipelineNamespaceRequest, TopLevelBrowsingContextId, WebViewId,
+};
+use base::Epoch;
 use bluetooth_traits::BluetoothRequest;
 use canvas_traits::canvas::{CanvasId, CanvasMsg};
 use canvas_traits::webgl::WebGLThreads;
@@ -113,7 +122,6 @@ use embedder_traits::{
 use euclid::default::Size2D as UntypedSize2D;
 use euclid::Size2D;
 use gfx::font_cache_thread::FontCacheThread;
-use gfx_traits::Epoch;
 use ipc_channel::ipc::{self, IpcReceiver, IpcSender};
 use ipc_channel::router::ROUTER;
 use ipc_channel::Error as IpcError;
@@ -121,12 +129,6 @@ use keyboard_types::webdriver::Event as WebDriverInputEvent;
 use keyboard_types::KeyboardEvent;
 use log::{debug, error, info, trace, warn};
 use media::{GLPlayerThreads, WindowGLContext};
-use msg::constellation_msg::{
-    BackgroundHangMonitorControlMsg, BackgroundHangMonitorRegister, BroadcastChannelRouterId,
-    BrowsingContextGroupId, BrowsingContextId, HangMonitorAlert, HistoryStateId, MessagePortId,
-    MessagePortRouterId, PipelineId, PipelineNamespace, PipelineNamespaceId,
-    PipelineNamespaceRequest, TopLevelBrowsingContextId, TraversalDirection, WebViewId,
-};
 use net_traits::pub_domains::reg_host;
 use net_traits::request::{Referrer, RequestBuilder};
 use net_traits::storage_thread::{StorageThreadMsg, StorageType};
@@ -142,8 +144,8 @@ use script_traits::{
     LoadData, LoadOrigin, LogEntry, MediaSessionActionType, MessagePortMsg, MouseEventType,
     PortMessageTask, SWManagerMsg, SWManagerSenders, ScriptMsg as FromScriptMsg,
     ScriptToConstellationChan, ServiceWorkerManagerFactory, ServiceWorkerMsg,
-    StructuredSerializedData, TimerSchedulerMsg, UpdatePipelineIdReason, WebDriverCommandMsg,
-    WindowSizeData, WindowSizeType,
+    StructuredSerializedData, TimerSchedulerMsg, TraversalDirection, UpdatePipelineIdReason,
+    WebDriverCommandMsg, WindowSizeData, WindowSizeType,
 };
 use serde::{Deserialize, Serialize};
 use servo_config::{opts, pref};
diff --git a/components/constellation/logging.rs b/components/constellation/logging.rs
index 672b63d1557..f2ca53d1f44 100644
--- a/components/constellation/logging.rs
+++ b/components/constellation/logging.rs
@@ -7,10 +7,10 @@ use std::sync::Arc;
 use std::thread;
 
 use backtrace::Backtrace;
+use base::id::TopLevelBrowsingContextId;
 use compositing_traits::ConstellationMsg as FromCompositorMsg;
 use crossbeam_channel::Sender;
 use log::{Level, LevelFilter, Log, Metadata, Record};
-use msg::constellation_msg::TopLevelBrowsingContextId;
 use parking_lot::ReentrantMutex;
 use script_traits::{LogEntry, ScriptMsg as FromScriptMsg, ScriptToConstellationChan};
 
diff --git a/components/constellation/network_listener.rs b/components/constellation/network_listener.rs
index a3dd8c11027..9ff19b32648 100644
--- a/components/constellation/network_listener.rs
+++ b/components/constellation/network_listener.rs
@@ -6,12 +6,12 @@
 //! Any redirects that are encountered are followed. Whenever a non-redirect
 //! response is received, it is forwarded to the appropriate script thread.
 
+use base::id::PipelineId;
 use crossbeam_channel::Sender;
 use http::HeaderMap;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use log::warn;
-use msg::constellation_msg::PipelineId;
 use net::http_loader::{set_default_accept, set_default_accept_language};
 use net_traits::request::{Destination, Referrer, RequestBuilder};
 use net_traits::response::ResponseInit;
diff --git a/components/constellation/pipeline.rs b/components/constellation/pipeline.rs
index 551c41929ca..000a52768ac 100644
--- a/components/constellation/pipeline.rs
+++ b/components/constellation/pipeline.rs
@@ -8,6 +8,14 @@ use std::rc::Rc;
 use std::sync::Arc;
 
 use background_hang_monitor::HangMonitorRegister;
+use background_hang_monitor_api::{
+    BackgroundHangMonitorControlMsg, BackgroundHangMonitorRegister, HangMonitorAlert,
+};
+use base::id::{
+    BrowsingContextId, HistoryStateId, PipelineId, PipelineNamespace, PipelineNamespaceId,
+    PipelineNamespaceRequest, TopLevelBrowsingContextId,
+};
+use base::Epoch;
 use bluetooth_traits::BluetoothRequest;
 use canvas_traits::webgl::WebGLPipeline;
 use compositing_traits::{CompositionPipeline, CompositorMsg, CompositorProxy};
@@ -15,17 +23,11 @@ use crossbeam_channel::{unbounded, Sender};
 use devtools_traits::{DevtoolsControlMsg, ScriptToDevtoolsControlMsg};
 use embedder_traits::EventLoopWaker;
 use gfx::font_cache_thread::FontCacheThread;
-use gfx_traits::Epoch;
 use ipc_channel::ipc::{self, IpcReceiver, IpcSender};
 use ipc_channel::router::ROUTER;
 use ipc_channel::Error;
 use log::{debug, error, warn};
 use media::WindowGLContext;
-use msg::constellation_msg::{
-    BackgroundHangMonitorControlMsg, BackgroundHangMonitorRegister, BrowsingContextId,
-    HangMonitorAlert, HistoryStateId, PipelineId, PipelineNamespace, PipelineNamespaceId,
-    PipelineNamespaceRequest, TopLevelBrowsingContextId,
-};
 use net::image_cache::ImageCacheImpl;
 use net_traits::image_cache::ImageCache;
 use net_traits::ResourceThreads;
diff --git a/components/constellation/session_history.rs b/components/constellation/session_history.rs
index 9e6f765ee15..7bd4ef2c288 100644
--- a/components/constellation/session_history.rs
+++ b/components/constellation/session_history.rs
@@ -5,11 +5,9 @@
 use std::cmp::PartialEq;
 use std::fmt;
 
+use base::id::{BrowsingContextId, HistoryStateId, PipelineId, TopLevelBrowsingContextId};
 use euclid::Size2D;
 use log::debug;
-use msg::constellation_msg::{
-    BrowsingContextId, HistoryStateId, PipelineId, TopLevelBrowsingContextId,
-};
 use script_traits::LoadData;
 use servo_url::ServoUrl;
 use style_traits::CSSPixel;
diff --git a/components/constellation/webview.rs b/components/constellation/webview.rs
index ddd51e31848..31d7937f9e2 100644
--- a/components/constellation/webview.rs
+++ b/components/constellation/webview.rs
@@ -4,7 +4,7 @@
 
 use std::collections::HashMap;
 
-use msg::constellation_msg::TopLevelBrowsingContextId;
+use base::id::TopLevelBrowsingContextId;
 
 #[derive(Debug)]
 pub struct WebViewManager<WebView> {
@@ -99,7 +99,7 @@ impl<WebView> WebViewManager<WebView> {
 mod test {
     use std::num::NonZeroU32;
 
-    use msg::constellation_msg::{
+    use base::id::{
         BrowsingContextId, BrowsingContextIndex, PipelineNamespace, PipelineNamespaceId,
         TopLevelBrowsingContextId, WebViewId,
     };