[regexp] Work around gcc bug triggering -Werror=strict-overflow

src/vector.h

 // Copyright 2014 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_VECTOR_H_
 #define V8_VECTOR_H_
 
 #include <string.h>
 #include <algorithm>
 
@@ skipping 33 matching lines @@
   int length() const { return length_; }
 
   // Returns whether or not the vector is empty.
   bool is_empty() const { return length_ == 0; }
 
   // Returns the pointer to the start of the data in the vector.
   T* start() const { return start_; }
 
   // Access individual vector elements - checks bounds in debug mode.
   T& operator[](int index) const {
-    DCHECK(0 <= index && index < length_);
+    DCHECK_LE(0, index);
+    DCHECK_LT(index, length_);
     return start_[index];
   }
 
   const T& at(int index) const { return operator[](index); }
 
   T& first() { return start_[0]; }
 
   T& last() { return start_[length_ - 1]; }
 
   typedef T* iterator;
@@ skipping 141 matching lines @@
 
 template <typename T, int N>
 inline Vector<T> ArrayVector(T (&arr)[N]) {
   return Vector<T>(arr);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_VECTOR_H_