Improve resilience of AbortSignals.

dom/abort/AbortSignal.cpp

@@ -56,9 +56,16 @@ AbortSignal::Aborted() const
 void
 AbortSignal::Abort()
 {
-  MOZ_ASSERT(!mAborted);
+  // Re-entrancy guard
+  if (mAborted) {
+    return;
+  }
   mAborted = true;
 
+  // We might be deleted as a result of aborting a follower, so ensure we
+  // stay alive until all followers have been aborted.
+  RefPtr<AbortSignal> pinThis = this;
+
   // Let's inform the followers.
   for (uint32_t i = 0; i < mFollowers.Length(); ++i) {
     mFollowers[i]->Aborted();

dom/abort/moz.build

@@ -14,7 +14,7 @@ EXPORTS.mozilla.dom += [
     'AbortSignal.h',
 ]
 
-UNIFIED_SOURCES += [
+SOURCES += [
     'AbortController.cpp',
     'AbortSignal.cpp',
 ]