Add a TurboFan skeleton for StringAddStub.

src/globals.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_GLOBALS_H_
 #define V8_GLOBALS_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 222 matching lines @@
   STRONG_BIT = 1 << 1,
   LANGUAGE_END,
 
   // Shorthands for some common language modes.
   SLOPPY = 0,
   STRICT = STRICT_BIT,
   STRONG = STRICT_BIT | STRONG_BIT
 };
 
 
-inline std::ostream& operator<<(std::ostream& os, LanguageMode mode) {
+inline std::ostream& operator<<(std::ostream& os, const LanguageMode& mode) {
   switch (mode) {
     case SLOPPY:
       return os << "sloppy";
     case STRICT:
       return os << "strict";
     case STRONG:
       return os << "strong";
     default:
       return os << "unknown";
   }
@@ skipping 185 matching lines @@
 const int kSpaceTagMask = (1 << kSpaceTagSize) - 1;
 
 enum AllocationAlignment { kWordAligned, kDoubleAligned, kDoubleUnaligned };
 
 // A flag that indicates whether objects should be pretenured when
 // allocated (allocated directly into the old generation) or not
 // (allocated in the young generation if the object size and type
 // allows).
 enum PretenureFlag { NOT_TENURED, TENURED };
 
+inline std::ostream& operator<<(std::ostream& os, const PretenureFlag& flag) {
+  switch (flag) {
+    case NOT_TENURED:
+      return os << "NotTenured";
+    case TENURED:
+      return os << "Tenured";
+  }
+  UNREACHABLE();
+  return os;
+}
+
 enum MinimumCapacity {
   USE_DEFAULT_MINIMUM_CAPACITY,
   USE_CUSTOM_MINIMUM_CAPACITY
 };
 
 enum GarbageCollector { SCAVENGER, MARK_COMPACTOR };
 
 enum Executability { NOT_EXECUTABLE, EXECUTABLE };
 
 enum VisitMode {
@@ skipping 469 matching lines @@
 inline FunctionKind WithObjectLiteralBit(FunctionKind kind) {
   kind = static_cast<FunctionKind>(kind | FunctionKind::kInObjectLiteral);
   DCHECK(IsValidFunctionKind(kind));
   return kind;
 }
 } }  // namespace v8::internal
 
 namespace i = v8::internal;
 
 #endif  // V8_GLOBALS_H_