Bug 1868410 - MSIX set to default browser takes too long r=nalexander,nrishel

This fix addresses cleanup work from https://phabricator.services.mozilla.com/D194828
It also makes it so that all file/protocol handlers get set with one launch of Powershell, to speed things up. Which it does. A lot.

It also:
* makes somethings use of nsString (where it was easy to do)
* moves the thread managing code out of SetDefaultBrowser.cpp and into DefaultAgent.cpp
* puts auto in a couple of places to make the code easier to read
* removes some logging statements in the powershell script code

Differential Revision: https://phabricator.services.mozilla.com/D195839

Author: mhughes-mozilla

browser/components/shell/WindowsUserChoice.cpp

@@ -284,6 +284,21 @@ UniquePtr<wchar_t[]> GetAssociationKeyPath(const wchar_t* aExt) {
   return keyPath;
 }
 
+nsresult AppendAssociationKeyPath(const wchar_t* aExt, nsString& output) {
+  if (aExt[0] == L'.') {
+    output.AppendLiteral(
+        u"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer\\FileExts\\");
+  } else {
+    output.AppendLiteral(
+        u"SOFTWARE\\Microsoft\\Windows\\Shell\\Associations\\UrlAssociations"
+        u"\\");
+  }
+
+  output.Append(aExt);
+
+  return NS_OK;
+}
+
 UniquePtr<wchar_t[]> GenerateUserChoiceHash(const wchar_t* aExt,
                                             const wchar_t* aUserSid,
                                             const wchar_t* aProgId,

browser/components/shell/WindowsUserChoice.h

@@ -10,6 +10,7 @@
 
 #include "ErrorList.h"  // for nsresult
 #include "mozilla/UniquePtr.h"
+#include "nsString.h"
 
 /*
  * Check the UserChoice Hashes for https, http, .html, .htm
@@ -60,6 +61,14 @@ CheckUserChoiceHashResult CheckUserChoiceHash(const wchar_t* aExt,
  */
 mozilla::UniquePtr<wchar_t[]> GetAssociationKeyPath(const wchar_t* aExt);
 
+/*
+ * Appends the registry path for the given association, file extension or
+ * protocol to the parameter string.
+ *
+ * @return The path, or nullptr on failure.
+ */
+nsresult AppendAssociationKeyPath(const wchar_t* aExt, nsString& output);
+
 /*
  * Get the current user's SID
  *

toolkit/mozapps/defaultagent/DefaultAgent.cpp

@@ -370,6 +370,10 @@ NS_IMETHODIMP
 DefaultAgent::SetDefaultBrowserUserChoiceAsync(
     const nsAString& aAumid, const nsTArray<nsString>& aExtraFileExtensions,
     JSContext* aCx, dom::Promise** aPromise) {
+  if (!NS_IsMainThread()) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
   ErrorResult rv;
   RefPtr<dom::Promise> promise =
       dom::Promise::Create(xpc::CurrentNativeGlobal(aCx), rv);
@@ -382,16 +386,29 @@ DefaultAgent::SetDefaultBrowserUserChoiceAsync(
   auto promiseHolder = MakeRefPtr<nsMainThreadPtrHolder<dom::Promise>>(
       "SetDefaultBrowserUserChoiceAsync promise", promise);
 
-  auto result = default_agent::SetDefaultBrowserUserChoiceAsync(
-      PromiseFlatString(aAumid).get(), aExtraFileExtensions,
-      [promiseHolder = std::move(promiseHolder)](nsresult result) {
-        dom::Promise* promise = promiseHolder.get()->get();
-        if (NS_SUCCEEDED(result)) {
-          promise->MaybeResolveWithUndefined();
-        } else {
-          promise->MaybeReject(result);
-        }
-      });
+  nsresult result = NS_DispatchBackgroundTask(
+      NS_NewRunnableFunction(
+          "SetDefaultBrowserUserChoiceAsync",
+          // Make a local copy of the aAudmid parameter which is a reference
+          // which will go out of scope
+          [aumid = nsString(aAumid), promiseHolder = std::move(promiseHolder),
+           aExtraFileExtensions =
+               CopyableTArray<nsString>(aExtraFileExtensions)] {
+            nsresult rv = default_agent::SetDefaultBrowserUserChoice(
+                PromiseFlatString(aumid).get(), aExtraFileExtensions);
+
+            NS_DispatchToMainThread(NS_NewRunnableFunction(
+                "SetDefaultBrowserUserChoiceAsync callback",
+                [rv, promiseHolder = std::move(promiseHolder)] {
+                  dom::Promise* promise = promiseHolder.get()->get();
+                  if (NS_SUCCEEDED(rv)) {
+                    promise->MaybeResolveWithUndefined();
+                  } else {
+                    promise->MaybeReject(rv);
+                  }
+                }));
+          }),
+      NS_DISPATCH_EVENT_MAY_BLOCK);
 
   promise.forget(aPromise);
   return result;