Use hash map to look for objects in the root array when serializing.

src/compiler.cc

Index: src/compiler.cc
diff --git a/src/compiler.cc b/src/compiler.cc
index 0e6c3a3867c95a824698396991b8d7e3d7c9e882..3c0b24378759553fc7fb7f259e8e31a5355bf3cf 100644
--- a/src/compiler.cc
+++ b/src/compiler.cc
@@ -1236,8 +1236,8 @@ Handle<SharedFunctionInfo> Compiler::CompileScript(
             isolate->counters()->compile_serialize());
         *cached_data = CodeSerializer::Serialize(isolate, result, source);
         if (FLAG_profile_deserialization) {
-          PrintF("[Compiling and serializing %d bytes took %0.3f ms]\n",
-                 (*cached_data)->length(), timer.Elapsed().InMillisecondsF());
+          PrintF("[Compiling and serializing took %0.3f ms]\n",
+                 timer.Elapsed().InMillisecondsF());
         }
       }
     }