[heap] Fix stack scan to include client Isolates

Stack scan during marking for shared heap broke in
  https://crrev.com/c/3703837

This CL re-adds the client Isolate handling which is necessary as
those client Isolates may refer to the shared Isolate from stack.

Bug: v8:13019
Change-Id: I1ee27fb8bab173087a98a0b79f4126612427b016
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3736444Reviewed-by: Nikolaos Papaspyrou <nikolaos@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81460}

src/heap/heap.cc

@@ -5082,9 +5082,12 @@ void Heap::IterateRootsIncludingClients(RootVisitor* v,
   }
 }
 
-void Heap::IterateRootsFromStack(RootVisitor* v) {
+void Heap::IterateRootsFromStackIncludingClient(RootVisitor* v) {
   IterateStackRoots(v);
-  v->Synchronize(VisitorSynchronization::kStackRoots);
+  if (isolate()->is_shared()) {
+    isolate()->global_safepoint()->IterateClientIsolates(
+        [v](Isolate* client) { client->heap()->IterateStackRoots(v); });
+  }
 }
 
 void Heap::IterateWeakGlobalHandles(RootVisitor* v) {

src/heap/heap.h

@@ -1057,7 +1057,7 @@ class Heap {
   void IterateRoots(RootVisitor* v, base::EnumSet<SkipRoot> options);
   void IterateRootsIncludingClients(RootVisitor* v,
                                     base::EnumSet<SkipRoot> options);
-  void IterateRootsFromStack(RootVisitor* v);
+  void IterateRootsFromStackIncludingClient(RootVisitor* v);
 
   // Iterates over entries in the smi roots list.  Only interesting to the
   // serializer/deserializer, since GC does not care about smis.

src/heap/mark-compact.cc

@@ -2145,7 +2145,7 @@ Address MarkCompactCollector::FindBasePtrForMarking(Address maybe_inner_ptr) {
 #endif  // V8_ENABLE_INNER_POINTER_RESOLUTION_MB
 
 void MarkCompactCollector::MarkRootsFromStack(RootVisitor* root_visitor) {
-  heap()->IterateRootsFromStack(root_visitor);
+  heap()->IterateRootsFromStackIncludingClient(root_visitor);
 }
 
 void MarkCompactCollector::MarkObjectsFromClientHeaps() {