Parallel and concurrent sweeping.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index b3cfb4327db2085b1f0934de8240e9f101de2e5e..202fa3d35dbf48599dd144b0f7c12cf78fe40a56 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -78,6 +78,7 @@ class UnicodeCache;
 class ConsStringIteratorOp;
 class StringTracker;
 class StubCache;
+class SweeperThread;
 class ThreadManager;
 class ThreadState;
 class ThreadVisitor;  // Defined in v8threads.h
@@ -1070,6 +1071,10 @@ class Isolate {
     return &optimizing_compiler_thread_;
   }
 
+  SweeperThread** sweeper_threads() {
+    return sweeper_thread_;
+  }
+
  private:
   Isolate();
 
@@ -1295,11 +1300,13 @@ class Isolate {
 
   DeferredHandles* deferred_handles_head_;
   OptimizingCompilerThread optimizing_compiler_thread_;
+  SweeperThread** sweeper_thread_;
 
   friend class ExecutionAccess;
   friend class HandleScopeImplementer;
   friend class IsolateInitializer;
   friend class OptimizingCompilerThread;
+  friend class SweeperThread;
   friend class ThreadManager;
   friend class Simulator;
   friend class StackGuard;