no-bug: Make sure to clear memory on shutdown

src/zen/boosts/actors/ZenBoostsParent.sys.mjs

@@ -16,6 +16,16 @@ export class ZenBoostsParent extends JSWindowActorParent {
     "zen-boosts-disable-picker",
   ];
 
+  // Topics the content child is allowed to forward to the observer service.
+  // Anything outside this set is rejected to prevent content-triggered
+  // notifications on unrelated chrome observers.
+  static ALLOWED_NOTIFY_TOPICS = new Set([
+    "zap-state-update",
+    "zap-list-update",
+    "selector-picker-state-update",
+    "selector-picker-picked",
+  ]);
+
   /**
    * Creates a new ZenBoostsParent actor instance and sets up an observer
    * for boost update notifications.
@@ -91,11 +101,14 @@ export class ZenBoostsParent extends JSWindowActorParent {
         break;
       }
       case "ZenBoost:Notify": {
-        Services.obs.notifyObservers(
-          null,
-          message.data.topic,
-          message.data.msg
-        );
+        const { topic, msg } = message.data ?? {};
+        if (!ZenBoostsParent.ALLOWED_NOTIFY_TOPICS.has(topic)) {
+          console.warn(
+            `[ZenBoostsParent]: Rejected notify for disallowed topic: ${topic}`
+          );
+          break;
+        }
+        Services.obs.notifyObservers(null, topic, msg);
         break;
       }
       case "ZenBoost:ZapSelector": {

src/zen/boosts/nsZenBoostsBackend.cpp

@@ -7,6 +7,7 @@
 #include "nsIXULRuntime.h"
 #include "nsPresContext.h"
 
+#include "mozilla/ClearOnShutdown.h"
 #include "mozilla/StaticPtr.h"
 
 #include "mozilla/ServoStyleConsts.h"
@@ -266,17 +267,19 @@ inline static void GetZenBoostsDataFromBrowsingContext(
 
 }  // namespace
 
+static mozilla::StaticAutoPtr<nsZenBoostsBackend> sZenBoostsBackend;
+
 auto nsZenBoostsBackend::GetInstance() -> nsZenBoostsBackend* {
-  static nsZenBoostsBackend* zenBoosts;
   if (!XRE_IsContentProcess()) {
     // Zen boosts are only supported in content, so if we're in the parent
     // process, just return null.
     return nullptr;
   }
-  if (!zenBoosts) {
-    zenBoosts = new nsZenBoostsBackend();
+  if (!sZenBoostsBackend) {
+    sZenBoostsBackend = new nsZenBoostsBackend();
+    mozilla::ClearOnShutdown(&sZenBoostsBackend);
   }
-  return zenBoosts;
+  return sZenBoostsBackend.get();
 }
 
 auto nsZenBoostsBackend::onPresShellEntered(mozilla::dom::Document* aDocument)
@@ -284,12 +287,8 @@ auto nsZenBoostsBackend::onPresShellEntered(mozilla::dom::Document* aDocument)
   // Note that aDocument can be null when entering anonymous content frames.
   // We explicitly do this to prevent applying boosts to anonymous content, such
   // as devtools or screenshots.
-  mozilla::dom::BrowsingContext* browsingContext =
+  mCurrentBrowsingContext =
       aDocument ? aDocument->GetBrowsingContext() : nullptr;
-  if (!browsingContext) {
-    return;
-  }
-  mCurrentBrowsingContext = browsingContext;
 }
 
 [[nodiscard]] ZEN_HOT_FUNCTION auto

src/zen/boosts/nsZenBoostsBackend.h

@@ -25,6 +25,7 @@ struct nsZenAccentOklab {
 class nsZenBoostsBackend final {
  public:
   explicit nsZenBoostsBackend() = default;
+  ~nsZenBoostsBackend() = default;
 
   /**
    * Indicates whether the current frame being rendered is for anonymous
@@ -64,8 +65,6 @@ class nsZenBoostsBackend final {
   }
 
  private:
-  ~nsZenBoostsBackend() = default;
-
   /**
    * The presshell of the current document being rendered.
    */