fixup! Bug 40933: Add tor-launcher functionality

Bug 41549: Correctly handle tor's stdout

Subprocess.jsm manages stdout through a pipe, which we never emptied.
As a result, it tor filled it completely, a lot of other stuff stalled.

The previous implementation dumped tor's stdout to the browser's one,
so this commit restores this behavior.

toolkit/components/tor-launcher/TorProcess.jsm

@@ -133,9 +133,10 @@ class TorProcess {
         arguments: this._args,
         environment,
         environmentAppend: true,
-        stderr: "pipe",
+        stderr: "stdout",
       };
       this._subprocess = await Subprocess.call(options);
+      this._dumpStdout();
       this._watchProcess();
       this._status = TorProcessStatus.Running;
       this._torProcessStartTime = Date.now();
@@ -173,6 +174,16 @@ class TorProcess {
     this._didConnectToTorControlPort = true;
   }
 
+  async _dumpStdout() {
+    let string;
+    while (
+      this._subprocess &&
+      (string = await this._subprocess.stdout.readString())
+    ) {
+      dump(string);
+    }
+  }
+
   async _watchProcess() {
     const watched = this._subprocess;
     if (!watched) {