Bug 1591564 - Use Rust string types with std::thread r=froydnj,janerik

The end of the std::thread at process end didn't seem to release the owned
nsStringBuffer in a way that refcounting liked. So let's copy the nsAString
into an owned String, move it into the thread's closure, and convert it as
necessary to an nsAString when we invoke pingsender.

Not the most efficient, but it doesn't have to be. This is prototype code
that will be removed.

Depends on D58809

Differential Revision: https://phabricator.services.mozilla.com/D59531

--HG--
extra : moz-landing-system : lando

toolkit/components/telemetry/fog/src/lib.rs

@@ -51,7 +51,7 @@ pub unsafe extern "C" fn fog_init(data_dir: &nsAString, pingsender_path: &nsAStr
 }
 
 fn prototype_ping_init(ping_dir: PathBuf, pingsender_path: &nsAString) -> Result<JoinHandle<()>, Error> {
-  let pingsender_path_owned = nsString::from(pingsender_path);
+  let pingsender_path = pingsender_path.to_string();
   thread::Builder::new().name("fogotype_ping".to_owned()).spawn(move || {
     let prototype_ping = PingType::new("prototype", true, true);
     glean_preview::register_ping_type(&prototype_ping);
@@ -65,14 +65,14 @@ fn prototype_ping_init(ping_dir: PathBuf, pingsender_path: &nsAString) -> Result
         continue;
       }
       prototype_ping.submit();
-      if let Err(e) = send_all_pings(&ping_dir, &pingsender_path_owned) {
+      if let Err(e) = send_all_pings(&ping_dir, &pingsender_path) {
         error!("Failed to send all pings due to {:?}", e);
       }
     }
   })
 }
 
-fn send_all_pings(ping_dir: &Path, pingsender_path: &nsAString) -> Result<(), Box<dyn std::error::Error>> {
+fn send_all_pings(ping_dir: &Path, pingsender_path: &str) -> Result<(), Box<dyn std::error::Error>> {
   assert!(ping_dir.is_dir());
   // This will be a multi-step process:
   // 1. Ensure we have an (empty) subdirectory in ping_dir called "telemetry" we can work within.
@@ -113,7 +113,7 @@ fn send_all_pings(ping_dir: &Path, pingsender_path: &nsAString) -> Result<(), Bo
     let pingsender_file: RefPtr<nsIFile>  = xpcom::create_instance(&cstr!("@mozilla.org/file/local;1")).ok_or("couldn't create nsIFile")?;
     let process: RefPtr<nsIProcess> = xpcom::create_instance(&cstr!("@mozilla.org/process/util;1")).ok_or("couldn't create nsIProcess")?;
     unsafe {
-      pingsender_file.InitWithPath(pingsender_path).to_result()?;
+      pingsender_file.InitWithPath(&*nsString::from(pingsender_path) as &nsAString).to_result()?;
       process.Init(&*pingsender_file).to_result()?;
       process.SetStartHidden(true).to_result()?;
       process.SetNoShell(true).to_result()?;