Avoid TLS accesses in Object::Lookup and Object::GetPrototype.

src/property.h

Index: src/property.h
diff --git a/src/property.h b/src/property.h
index e79c87e6d9343b776ad564c144a3fecbe4970662..0500e57ae48ff093566f640b9ecc246fb5199fab 100644
--- a/src/property.h
+++ b/src/property.h
@@ -183,10 +183,12 @@ class LookupResult BASE_EMBEDDED {
   }
 
   ~LookupResult() {
-    ASSERT(isolate_->top_lookup_result() == this);
-    isolate_->SetTopLookupResult(next_);
+    ASSERT(isolate()->top_lookup_result() == this);
+    isolate()->SetTopLookupResult(next_);
   }
 
+  Isolate* isolate() const { return isolate_; }
+
   void DescriptorResult(JSObject* holder, PropertyDetails details, int number) {
     lookup_type_ = DESCRIPTOR_TYPE;
     holder_ = holder;
@@ -342,7 +344,7 @@ class LookupResult BASE_EMBEDDED {
       case INTERCEPTOR:
       case TRANSITION:
       case NONEXISTENT:
-        return Isolate::Current()->heap()->the_hole_value();
+        return isolate()->heap()->the_hole_value();
     }
     UNREACHABLE();
     return NULL;