Don't use ConsStringIterator to compute string hashes

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 09ca02854f12282e81d70327209e7c0f52f1c903..6f19075ac5b9e02eb1084891028b9238078396c9 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1635,6 +1635,7 @@ Isolate::Isolate(bool enable_serializer)
       thread_manager_(NULL),
       has_installed_extensions_(false),
       string_tracker_(NULL),
+      cons_string_hashing_buffer_(nullptr),
       regexp_stack_(NULL),
       date_cache_(NULL),
       call_descriptor_data_(NULL),
@@ -1881,6 +1882,9 @@ Isolate::~Isolate() {
   delete eternal_handles_;
   eternal_handles_ = NULL;
 
+  delete[] cons_string_hashing_buffer_;
+  cons_string_hashing_buffer_ = nullptr;
+
   delete string_stream_debug_object_cache_;
   string_stream_debug_object_cache_ = NULL;
 
@@ -1996,6 +2000,7 @@ bool Isolate::Init(Deserializer* des) {
   handle_scope_implementer_ = new HandleScopeImplementer(this);
   stub_cache_ = new StubCache(this);
   materialized_object_store_ = new MaterializedObjectStore(this);
+  cons_string_hashing_buffer_ = new uint16_t[String::kMaxHashCalcLength];
   regexp_stack_ = new RegExpStack();
   regexp_stack_->isolate_ = this;
   date_cache_ = new DateCache();