[regexp] do not assume short external strings have a minimum size.

src/objects.h

 // Copyright 2015 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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/assert-scope.h"
@@ skipping 9220 matching lines @@
 class ExternalString: public String {
  public:
   DECLARE_CAST(ExternalString)
 
   // Layout description.
   static const int kResourceOffset = POINTER_SIZE_ALIGN(String::kSize);
   static const int kShortSize = kResourceOffset + kPointerSize;
   static const int kResourceDataOffset = kResourceOffset + kPointerSize;
   static const int kSize = kResourceDataOffset + kPointerSize;
 
-  static const int kMaxShortLength =
-      (kShortSize - SeqString::kHeaderSize) / kCharSize;
-
   // Return whether external string is short (data pointer is not cached).
   inline bool is_short();
 
   STATIC_ASSERT(kResourceOffset == Internals::kStringResourceOffset);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(ExternalString);
 };
 
 
@@ skipping 1542 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_