Auto merge of #23204 - jdm:media-backend-init, r=Manishearth

Move media backend initialization to process startup

This makes tinkering with the gstreamer backend _way_ more efficient, because it is no longer necessary to rebuild the script crate after every change.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23127
- [x] There are tests for these changes

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---
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components/script/Cargo.toml

@@ -97,7 +97,6 @@ servo_atoms = {path = "../atoms"}
 servo_config = {path = "../config"}
 servo_geometry = {path = "../geometry" }
 servo-media = {git = "https://github.com/servo/media"}
-servo-media-auto = {git = "https://github.com/servo/media"}
 servo_rand = {path = "../rand"}
 servo_url = {path = "../url"}
 smallvec = { version = "0.6", features = ["std", "union"] }

components/script/dom/baseaudiocontext.rs

@@ -51,7 +51,6 @@ use servo_media::audio::context::{OfflineAudioContextOptions, RealTimeAudioConte
 use servo_media::audio::decoder::AudioDecoderCallbacks;
 use servo_media::audio::graph::NodeId;
 use servo_media::ServoMedia;
-use servo_media_auto::Backend;
 use std::cell::Cell;
 use std::collections::{HashMap, VecDeque};
 use std::mem;
@@ -109,8 +108,6 @@ impl BaseAudioContext {
             },
         };
 
-        ServoMedia::init::<Backend>();
-
         let context = BaseAudioContext {
             eventtarget: EventTarget::new_inherited(),
             audio_context_impl: ServoMedia::get()

components/script/dom/htmlmediaelement.rs

@@ -72,7 +72,6 @@ use servo_config::pref;
 use servo_media::player::frame::{Frame, FrameRenderer};
 use servo_media::player::{PlaybackState, Player, PlayerError, PlayerEvent, StreamType};
 use servo_media::ServoMedia;
-use servo_media_auto::Backend;
 use servo_url::ServoUrl;
 use std::cell::Cell;
 use std::collections::VecDeque;
@@ -276,7 +275,6 @@ pub enum ReadyState {
 
 impl HTMLMediaElement {
     pub fn new_inherited(tag_name: LocalName, prefix: Option<Prefix>, document: &Document) -> Self {
-        ServoMedia::init::<Backend>();
         Self {
             htmlelement: HTMLElement::new_inherited(tag_name, prefix, document),
             network_state: Cell::new(NetworkState::Empty),

components/script/dom/mediadevices.rs

@@ -17,7 +17,6 @@ use crate::dom::promise::Promise;
 use dom_struct::dom_struct;
 use servo_media::streams::capture::{Constrain, ConstrainRange, MediaTrackConstraintSet};
 use servo_media::ServoMedia;
-use servo_media_auto::Backend;
 use std::rc::Rc;
 
 #[dom_struct]
@@ -27,7 +26,6 @@ pub struct MediaDevices {
 
 impl MediaDevices {
     pub fn new_inherited() -> MediaDevices {
-        ServoMedia::init::<Backend>();
         MediaDevices {
             eventtarget: EventTarget::new_inherited(),
         }

components/script/dom/rtcpeerconnection.rs

@@ -41,7 +41,6 @@ use servo_media::webrtc::{
     SignalingState, WebRtcController, WebRtcSignaller,
 };
 use servo_media::ServoMedia;
-use servo_media_auto::Backend;
 
 use std::cell::Cell;
 use std::rc::Rc;
@@ -159,7 +158,6 @@ impl RTCPeerConnection {
             RTCPeerConnectionBinding::Wrap,
         );
         let signaller = this.make_signaller();
-        ServoMedia::init::<Backend>();
         *this.controller.borrow_mut() = Some(ServoMedia::get().unwrap().create_webrtc(signaller));
         if let Some(ref servers) = config.iceServers {
             if let Some(ref server) = servers.get(0) {

components/servo/Cargo.toml

@@ -65,6 +65,8 @@ script_layout_interface = {path = "../script_layout_interface"}
 script_traits = {path = "../script_traits"}
 servo_config = {path = "../config"}
 servo_geometry = {path = "../geometry"}
+servo-media = {git = "https://github.com/servo/media"}
+servo-media-auto = {git = "https://github.com/servo/media"}
 servo_url = {path = "../url"}
 style = {path = "../style", features = ["servo"]}
 style_traits = {path = "../style_traits", features = ["servo"]}

components/servo/lib.rs

@@ -103,6 +103,8 @@ use profile_traits::time;
 use script_traits::{ConstellationMsg, SWManagerSenders, ScriptToConstellationChan};
 use servo_config::opts;
 use servo_config::{pref, prefs};
+use servo_media::ServoMedia;
+use servo_media_auto::Backend;
 use std::borrow::Cow;
 use std::cmp::max;
 use std::path::PathBuf;
@@ -182,6 +184,10 @@ where
         // Global configuration options, parsed from the command line.
         let opts = opts::get();
 
+        if !opts.multiprocess {
+            ServoMedia::init::<Backend>();
+        }
+
         // Make sure the gl context is made current.
         window.prepare_for_composite();
 
@@ -751,6 +757,8 @@ pub fn run_content_process(token: String) {
     script::init();
     script::init_service_workers(sw_senders);
 
+    ServoMedia::init::<Backend>();
+
     unprivileged_content.start_all::<script_layout_interface::message::Msg,
                                      layout_thread::LayoutThread,
                                      script::script_thread::ScriptThread>(