Fix issues with FF first-run setup in OSX, and disable it in Windows

Previously this only worked in Linux. In Windows, it launches a child
process, so we can never get the right pid, so we can't reliably kill it
and tidy up as we'd like, and the two-step startup *requires* this, or
the second step fails with an error.

On Mac, we had a similar problem, but actually it turns out we just
needed to wait properly for the exit to propagate and shut everything
down. There is a child process (open -a ...), but it shuts down ok
anyway.

Author: pimterry

src/interceptors/fresh-firefox.ts

@@ -133,6 +133,7 @@ export class FreshFirefox implements Interceptor {
         certInstallBrowser.process.once('close', () => {
             certCheckServer.stop();
             certInstallBrowser = undefined;
+
             if (certInstalled !== true) {
                 reportError('Firefox certificate setup failed');
                 deleteFolder(this.firefoxProfilePath).catch(console.warn);
@@ -142,8 +143,14 @@ export class FreshFirefox implements Interceptor {
         await certInstalled;
         certInstalled = true;
 
-        await delay(100); // Tiny delay, so firefox can do initial setup tasks
+        await delay(200); // Tiny delay, so firefox can do initial setup tasks
+
+        // Tell firefox to shutdown, and wait until it does.
         certInstallBrowser.stop();
+        return new Promise((resolve) => {
+            if (!certInstallBrowser) return resolve();
+            else certInstallBrowser.process.once('close', resolve);
+        });
     }
 
     async activate(proxyPort: number) {
@@ -153,14 +160,14 @@ export class FreshFirefox implements Interceptor {
 
         let existingPrefs: _.Dictionary<any> = {};
 
-        if (await canAccess(firefoxPrefsFile) === false && process.platform !== 'darwin') {
+        if (await canAccess(firefoxPrefsFile) === false && process.platform !== 'win32') {
             /*
             First time, we do a separate pre-usage startup & stop, without the proxy, for certificate setup.
             This helps avoid initial Firefox profile setup request noise, and tidies up some awkward UX where
             firefox likes to open extra welcome windows/tabs on first run.
 
-            Unfortunately, OSX doesn't seem to play nicely with this, so we have to fall back to normal
-            behaviour in that case.
+            Unfortunately, Windows doesn't seem to play nicely with this (because it spawns separate child
+            processes that we can't reliable kill), so we have to fall back to normal behaviour in that case.
             */
             await this.setupFirefoxProfile();
         }