Migrate stack resource unwinding to Thread.

runtime/vm/allocation.cc

Index: runtime/vm/allocation.cc
diff --git a/runtime/vm/allocation.cc b/runtime/vm/allocation.cc
index b6ca73e10ff4c731729644ebfa673d682c6eafd8..92e288539d8b91aef7d0bb4efba8279d6ff6cb37 100644
--- a/runtime/vm/allocation.cc
+++ b/runtime/vm/allocation.cc
@@ -30,11 +30,11 @@ void* ZoneAllocated::operator new(uword size, Zone* zone) {
 }
 
 
-void StackResource::UnwindAbove(Isolate* isolate, StackResource* new_top) {
-  StackResource* current_resource = isolate->top_resource();
+void StackResource::UnwindAbove(Thread* thread, StackResource* new_top) {
+  StackResource* current_resource = thread->top_resource();
   while (current_resource != new_top) {
     current_resource->~StackResource();
-    current_resource = isolate->top_resource();
+    current_resource = thread->top_resource();
   }
 }