Make sure to initialize all fields in the special maps

created during bootstrapping. Without this change we 
risk having weird flags set on the map for the null
value (among others), which can lead to crashes.
Review URL: http://codereview.chromium.org/552195

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3725 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.cc

@@ -1185,7 +1185,10 @@ Object* Heap::AllocatePartialMap(InstanceType instance_type,
   reinterpret_cast<Map*>(result)->set_instance_type(instance_type);
   reinterpret_cast<Map*>(result)->set_instance_size(instance_size);
   reinterpret_cast<Map*>(result)->set_inobject_properties(0);
+  reinterpret_cast<Map*>(result)->set_pre_allocated_property_fields(0);
   reinterpret_cast<Map*>(result)->set_unused_property_fields(0);
+  reinterpret_cast<Map*>(result)->set_bit_field(0);
+  reinterpret_cast<Map*>(result)->set_bit_field2(0);
   return result;
 }