[turbofan] Improve JSON output

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 402010e91a7d8058eb9d45971cdcc2e27f60dbb3..88ced6c4438e9bc587f5c262fdfc872fe342405d 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -7521,6 +7521,49 @@ Object* JSMapIterator::CurrentValue() {
 }
 
 
+class String::SubStringRange::iterator FINAL {
+ public:
+  typedef std::forward_iterator_tag iterator_category;
+  typedef int difference_type;
+  typedef uc16 value_type;
+  typedef uc16* pointer;
+  typedef uc16& reference;
+
+  iterator(const iterator& other)
+      : content_(other.content_), offset_(other.offset_) {}
+
+  uc16 operator*() { return content_.Get(offset_); }
+  bool operator==(const iterator& other) const {
+    return content_.UsesSameString(other.content_) && offset_ == other.offset_;
+  }
+  bool operator!=(const iterator& other) const {
+    return !content_.UsesSameString(other.content_) || offset_ != other.offset_;
+  }
+  iterator& operator++() {
+    ++offset_;
+    return *this;
+  }
+  iterator operator++(int);
+
+ private:
+  friend class String;
+  iterator(String* from, int offset)
+      : content_(from->GetFlatContent()), offset_(offset) {}
+  String::FlatContent content_;
+  int offset_;
+};
+
+
+String::SubStringRange::iterator String::SubStringRange::begin() {
+  return String::SubStringRange::iterator(string_, first_);
+}
+
+
+String::SubStringRange::iterator String::SubStringRange::end() {
+  return String::SubStringRange::iterator(string_, first_ + length_);
+}
+
+
 #undef TYPE_CHECKER
 #undef CAST_ACCESSOR
 #undef INT_ACCESSORS