[wasm] Managed<T> ensures T's lifetime does not leak past Isolate's

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index ec52183cdf9c6ce009782ca847edafc218da96da..444d99feb8ce0205affb1214edd19bd39521021f 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -533,6 +533,8 @@ class Isolate {
   // for legacy API reasons.
   void TearDown();
 
+  void ReleaseManagedObjects();
+
   static void GlobalTearDown();
 
   void ClearSerializerData();
@@ -1208,6 +1210,39 @@ class Isolate {
   void set_allow_atomics_wait(bool set) { allow_atomics_wait_ = set; }
   bool allow_atomics_wait() { return allow_atomics_wait_; }
 
+  // List of native heap values allocated by the runtime as part of its
+  // implementation that must be freed at isolate deinit.
+  class ManagedObjectFinalizer final {
+   public:
+    typedef void (*Deleter)(void*);
+    void Dispose() { deleter_(value_); }
+
+   private:
+    friend class Isolate;
+
+    ManagedObjectFinalizer() {
+      DCHECK_EQ(reinterpret_cast<void*>(this),
+                reinterpret_cast<void*>(&value_));
+    }
+
+    // value_ must be the first member
+    void* value_ = nullptr;
+    Deleter deleter_ = nullptr;
+    ManagedObjectFinalizer* prev_ = nullptr;
+    ManagedObjectFinalizer* next_ = nullptr;
+  };
+
+  // Register a native value for destruction at isolate teardown.
+  ManagedObjectFinalizer* RegisterForReleaseAtTeardown(
+      void* value, ManagedObjectFinalizer::Deleter deleter);
+
+  // Unregister a previously registered value from release at
+  // isolate teardown, deleting the ManagedObjectFinalizer.
+  // This transfers the responsibility of the previously managed value's
+  // deletion to the caller. Pass by pointer, because *finalizer_ptr gets
+  // reset to nullptr.
+  void UnregisterFromReleaseAtTeardown(ManagedObjectFinalizer** finalizer_ptr);
+
  protected:
   explicit Isolate(bool enable_serializer);
   bool IsArrayOrObjectPrototype(Object* object);
@@ -1489,6 +1524,8 @@ class Isolate {
 
   bool allow_atomics_wait_;
 
+  ManagedObjectFinalizer managed_object_finalizers_list_;
+
   size_t total_regexp_code_generated_;
 
   friend class ExecutionAccess;