Fix two-char hash to use correct fallback for zero hashes.

src/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2695 matching lines @@
     roots_[constant_symbol_table[i].index] = String::cast(obj);
   }
 
   // Allocate the hidden symbol which is used to identify the hidden properties
   // in JSObjects. The hash code has a special value so that it will not match
   // the empty string when searching for the property. It cannot be part of the
   // loop above because it needs to be allocated manually with the special
   // hash code in place. The hash code for the hidden_symbol is zero to ensure
   // that it will always be at the first entry in property descriptors.
   { MaybeObject* maybe_obj =
-        AllocateSymbol(CStrVector(""), 0, String::kZeroHash);
+        AllocateSymbol(CStrVector(""), 0, String::kEmptyStringHash);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   hidden_symbol_ = String::cast(obj);
 
   // Allocate the foreign for __proto__.
   { MaybeObject* maybe_obj =
         AllocateForeign((Address) &Accessors::ObjectPrototype);
     if (!maybe_obj->ToObject(&obj)) return false;
   }
   set_prototype_accessors(Foreign::cast(obj));
@@ skipping 4611 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   FIXED_ARRAY_SUB_INSTANCE_TYPE_LIST(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   memcpy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   memcpy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 
 } }  // namespace v8::internal