Added support for isolate unhandled exceptions.

runtime/vm/object_store.h

Index: runtime/vm/object_store.h
diff --git a/runtime/vm/object_store.h b/runtime/vm/object_store.h
index ba7b09fc529258b55bd8d84a9aa424db981e71de..f94962b6a57557123ae30c64a07f10a26e8a31e7 100644
--- a/runtime/vm/object_store.h
+++ b/runtime/vm/object_store.h
@@ -421,6 +421,14 @@ class ObjectStore {
   }
   void clear_sticky_error() { sticky_error_ = Error::null(); }
 
+  RawInstance* unhandled_exception_closure() const {
+    return unhandled_exception_closure_;
+  }
+  void set_unhandled_exception_closure(const Instance& value) {
+    ASSERT(!value.IsNull());
+    unhandled_exception_closure_ = value.raw();
+  }
+
   RawBool* true_value() const { return true_value_; }
   void set_true_value(const Bool& value) { true_value_ = value.raw(); }
 
@@ -532,6 +540,7 @@ class ObjectStore {
   RawGrowableObjectArray* libraries_;
   RawGrowableObjectArray* pending_classes_;
   RawError* sticky_error_;
+  RawInstance* unhandled_exception_closure_;
   RawContext* empty_context_;
   RawInstance* stack_overflow_;
   RawInstance* out_of_memory_;