Add initial hydrogenized NewStringAddStub.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 15f307783b90718525ddd747f6a1d41fd0a30611..9a7a4e8553543350d29053cd890231d5c2b885e9 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -5804,6 +5804,12 @@ class HObjectAccess V8_FINAL {
         FLAG_track_fields ? Representation::Smi() : Representation::Tagged());
   }
 
+  static HObjectAccess ForStringHashField() {
+    return HObjectAccess(kInobject,
+                         String::kHashFieldOffset,
+                         Representation::Integer32());
+  }
+
   static HObjectAccess ForStringLength() {
     STATIC_ASSERT(String::kMaxLength <= Smi::kMaxValue);
     return HObjectAccess(
@@ -5812,6 +5818,14 @@ class HObjectAccess V8_FINAL {
         FLAG_track_fields ? Representation::Smi() : Representation::Tagged());
   }
 
+  static HObjectAccess ForConsStringFirst() {
+    return HObjectAccess(kInobject, ConsString::kFirstOffset);
+  }
+
+  static HObjectAccess ForConsStringSecond() {
+    return HObjectAccess(kInobject, ConsString::kSecondOffset);
+  }
+
   static HObjectAccess ForPropertiesPointer() {
     return HObjectAccess(kInobject, JSObject::kPropertiesOffset);
   }
@@ -5859,6 +5873,12 @@ class HObjectAccess V8_FINAL {
                          Representation::Byte());
   }
 
+  static HObjectAccess ForMapInstanceType() {
+    return HObjectAccess(kInobject,
+                         Map::kInstanceTypeOffset,
+                         Representation::Byte());
+  }
+
   static HObjectAccess ForPropertyCellValue() {
     return HObjectAccess(kInobject, PropertyCell::kValueOffset);
   }