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 b9c0ca9fce3d3e67b3e3a7f6b050c7f2f3ae6376..d2ae9750766cfba4d1ff8c86eb8248b541a59590 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -5808,6 +5808,12 @@ 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(
@@ -5816,6 +5822,14 @@ 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);
   }
@@ -5863,6 +5877,12 @@ class HObjectAccess V8_FINAL {
                          Representation::UInteger8());
   }
 
+  static HObjectAccess ForMapInstanceType() {
+    return HObjectAccess(kInobject,
+                         Map::kInstanceTypeOffset,
+                         Representation::UInteger8());
+  }
+
   static HObjectAccess ForPropertyCellValue() {
     return HObjectAccess(kInobject, PropertyCell::kValueOffset);
   }