Auto merge of #16477 - sadmansk:url_param_browser, r=paulrouget

Pass URL to Browser::new(), delegate url checking logic to 3rd party

<!-- Please describe your changes on the following line: -->
1. Move the logic of computing the initial url from `opts.rs` to `/ports/servo/main.rs`
2. Add a `ServoUrl` argument to `Browser::new`

Based on the requested changes by @paulrouget:
>We can read the pref in main() instead. shell.homepage would be used if the url is not passed as an argument. I'm trying to decouple the "app" logic and the "web engine" logic. I think it's up to the app to set the initial URL, and I'm not sure the initial url should be part of opts.

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #15636

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- [ ] There are tests for these changes

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components/config/opts.rs

@@ -480,7 +480,7 @@ const DEFAULT_USER_AGENT: UserAgent = UserAgent::Desktop;
 pub fn default_opts() -> Opts {
     Opts {
         is_running_problem_test: false,
-        url: Some(ServoUrl::parse("about:blank").unwrap()),
+        url: None,
         tile_size: 512,
         device_pixels_per_px: None,
         time_profiling: None,
@@ -631,11 +631,10 @@ pub fn from_cmdline_args(args: &[String]) -> ArgumentParsingResult {
     }
 
     let cwd = env::current_dir().unwrap();
-    let homepage_pref = PREFS.get("shell.homepage");
     let url_opt = if !opt_match.free.is_empty() {
         Some(&opt_match.free[0][..])
     } else {
-        homepage_pref.as_string()
+        None
     };
     let is_running_problem_test =
         url_opt
@@ -645,16 +644,11 @@ pub fn from_cmdline_args(args: &[String]) -> ArgumentParsingResult {
              url.starts_with("http://web-platform.test:8000/_mozilla/mozilla/canvas/") ||
              url.starts_with("http://web-platform.test:8000/_mozilla/css/canvas_over_area.html"));
 
-    let url = match url_opt {
-        Some(url_string) => {
-            parse_url_or_filename(&cwd, url_string)
-                .unwrap_or_else(|()| args_fail("URL parsing failed"))
-        },
-        None => {
-            print_usage(app_name, &opts);
-            args_fail("servo asks that you provide a URL")
-        }
-    };
+    let url_opt = url_opt.and_then(|url_string| parse_url_or_filename(&cwd, url_string)
+                                   .or_else(|error| {
+                                       warn!("URL parsing failed ({:?}).", error);
+                                       Err(error)
+                                   }).ok());
 
     let tile_size: usize = match opt_match.opt_str("s") {
         Some(tile_size_str) => tile_size_str.parse()
@@ -775,7 +769,7 @@ pub fn from_cmdline_args(args: &[String]) -> ArgumentParsingResult {
 
     let opts = Opts {
         is_running_problem_test: is_running_problem_test,
-        url: Some(url),
+        url: url_opt,
         tile_size: tile_size,
         device_pixels_per_px: device_pixels_per_px,
         time_profiling: time_profiling,

components/servo/lib.rs

@@ -122,7 +122,7 @@ pub struct Browser<Window: WindowMethods + 'static> {
 }
 
 impl<Window> Browser<Window> where Window: WindowMethods + 'static {
-    pub fn new(window: Rc<Window>) -> Browser<Window> {
+    pub fn new(window: Rc<Window>, target_url: ServoUrl) -> Browser<Window> {
         // Global configuration options, parsed from the command line.
         let opts = opts::get();
 
@@ -203,7 +203,7 @@ impl<Window> Browser<Window> where Window: WindowMethods + 'static {
         // as the navigation context.
         let (constellation_chan, sw_senders) = create_constellation(opts.user_agent.clone(),
                                                                     opts.config_dir.clone(),
-                                                                    opts.url.clone(),
+                                                                    target_url,
                                                                     compositor_proxy.clone_compositor_proxy(),
                                                                     time_profiler_chan.clone(),
                                                                     mem_profiler_chan.clone(),
@@ -287,7 +287,7 @@ fn create_compositor_channel(event_loop_waker: Box<compositor_thread::EventLoopW
 
 fn create_constellation(user_agent: Cow<'static, str>,
                         config_dir: Option<PathBuf>,
-                        url: Option<ServoUrl>,
+                        url: ServoUrl,
                         compositor_proxy: CompositorProxy,
                         time_profiler_chan: time::ProfilerChan,
                         mem_profiler_chan: mem::ProfilerChan,
@@ -337,9 +337,7 @@ fn create_constellation(user_agent: Cow<'static, str>,
         constellation_chan.send(ConstellationMsg::SetWebVRThread(webvr_thread)).unwrap();
     }
 
-    if let Some(url) = url {
-        constellation_chan.send(ConstellationMsg::InitLoadUrl(url)).unwrap();
-    };
+    constellation_chan.send(ConstellationMsg::InitLoadUrl(url)).unwrap();
 
     // channels to communicate with Service Worker Manager
     let sw_senders = SWManagerSenders {