Per-isolate v8::Locker and v8::Unlocker

src/api.h

Index: src/api.h
diff --git a/src/api.h b/src/api.h
index 7423d28e2f807d9947604f7dc1503bb72d7aaf36..6ea2df906a3c894dc64dac355146ae744a11620e 100644
--- a/src/api.h
+++ b/src/api.h
@@ -399,8 +399,9 @@ class StringTracker {
 ISOLATED_CLASS HandleScopeImplementer {
  public:
 
-  HandleScopeImplementer()
-      : blocks_(0),
+  explicit HandleScopeImplementer(Isolate* isolate)
+      : isolate_(isolate),
+        blocks_(0),
         entered_contexts_(0),
         saved_contexts_(0),
         spare_(NULL),
@@ -466,6 +467,7 @@ ISOLATED_CLASS HandleScopeImplementer {
     ASSERT(call_depth_ == 0);
   }
 
+  Isolate* isolate_;
   List<internal::Object**> blocks_;
   // Used as a stack to keep track of entered contexts.
   List<Handle<Object> > entered_contexts_;