Safepointing in GC

runtime/vm/gc_sweeper.h

Index: runtime/vm/gc_sweeper.h
diff --git a/runtime/vm/gc_sweeper.h b/runtime/vm/gc_sweeper.h
index b2b831749b57a660b47386deccfacf95956a630a..842c6d9512b446806983409e495c0caeedebf4de 100644
--- a/runtime/vm/gc_sweeper.h
+++ b/runtime/vm/gc_sweeper.h
@@ -6,6 +6,7 @@
 #define VM_GC_SWEEPER_H_
 
 #include "vm/globals.h"
+#include "vm/thread.h"
 
 namespace dart {
 
@@ -35,10 +36,13 @@ class GCSweeper {
   intptr_t SweepLargePage(HeapPage* page);
 
   // Sweep the regular sized data pages between first and last inclusive.
+  // Waits for the concurrent sweeper task to enter the isolate before
+  // returning to the caller.
   static void SweepConcurrent(Isolate* isolate,
                               HeapPage* first,
                               HeapPage* last,
-                              FreeList* freelist);
+                              FreeList* freelist,
+                              SafepointId pass_safepoint);
 };
 
 }  // namespace dart