[wasm] Use two-pass phantom callbacks for managed objects.

The phantom handle API requires that the first pass callback does not
invoke any V8 API. The current code breaks this requirement by invoking
AdjustAmountOfExternalAllocatedMemory, which can cause GC.

This patch splits the existing callback into two parts. The first part
only resets the handle and the second part performs native delete.

Bug: chromium:827806
Change-Id: I01eed09f94f5499cb9d13397066f4f908a0aa668
Reviewed-on: https://chromium-review.googlesource.com/995796
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52366}

src/managed.h

@@ -59,22 +59,30 @@ class Managed : public Foreign {
         isolate->factory()->NewForeign(reinterpret_cast<Address>(finalizer)));
     Handle<Object> global_handle = isolate->global_handles()->Create(*handle);
     finalizer->global_handle_location = global_handle.location();
-    GlobalHandles::MakeWeak(finalizer->global_handle_location,
-                            handle->GetFinalizer(), &Managed<CppType>::GCDelete,
-                            v8::WeakCallbackType::kParameter);
+    GlobalHandles::MakeWeak(
+        finalizer->global_handle_location, handle->GetFinalizer(),
+        &ResetWeakAndScheduleGCDelete, v8::WeakCallbackType::kParameter);
 
     return handle;
   }
 
  private:
-  static void GCDelete(const v8::WeakCallbackInfo<void>& data) {
+  static void ResetWeakAndScheduleGCDelete(
+      const v8::WeakCallbackInfo<void>& data) {
     FinalizerWithHandle* finalizer =
         reinterpret_cast<FinalizerWithHandle*>(data.GetParameter());
-
+    GlobalHandles::Destroy(finalizer->global_handle_location);
     Isolate* isolate = reinterpret_cast<Isolate*>(data.GetIsolate());
     isolate->UnregisterFromReleaseAtTeardown(finalizer);
+    // We need to call GCDelete as a second pass callback because
+    // it can trigger garbage collection. The first pass callbacks
+    // are not allowed to invoke V8 API.
+    data.SetSecondPassCallback(&GCDelete);
+  }
 
-    GlobalHandles::Destroy(finalizer->global_handle_location);
+  static void GCDelete(const v8::WeakCallbackInfo<void>& data) {
+    FinalizerWithHandle* finalizer =
+        reinterpret_cast<FinalizerWithHandle*>(data.GetParameter());
     NativeDelete(finalizer);
   }