Clean up is-ASCII checks.

src/string-search.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 48 matching lines @@
   // Bad-char shift table stored in the state. It's length is the alphabet size.
   // For patterns below this length, the skip length of Boyer-Moore is too short
   // to compensate for the algorithmic overhead compared to simple brute force.
   static const int kBMMinPatternLength = 7;
 
   static inline bool IsAsciiString(Vector<const char>) {
     return true;
   }
 
   static inline bool IsAsciiString(Vector<const uc16> string) {
-    for (int i = 0, n = string.length(); i < n; i++) {
-      if (static_cast<unsigned>(string[i]) > String::kMaxAsciiCharCodeU) {
-        return false;
-      }
-    }
-    return true;
+    return String::IsAscii(string.start(), string.length());
   }
 
   // The following tables are shared by all searches.
   // TODO(lrn): Introduce a way for a pattern to keep its tables
   // between searches (e.g., for an Atom RegExp).
 
   // Store for the BoyerMoore(Horspool) bad char shift table.
   static int kBadCharShiftTable[kUC16AlphabetSize];
   // Store for the BoyerMoore good suffix shift table.
   static int kGoodSuffixShiftTable[kBMMaxShift + 1];
@@ skipping 478 matching lines @@
 static int SearchString(Vector<const SubjectChar> subject,
                         Vector<const PatternChar> pattern,
                         int start_index) {
   StringSearch<PatternChar, SubjectChar> search(pattern);
   return search.Search(subject, start_index);
 }
 
 }}  // namespace v8::internal
 
 #endif  // V8_STRING_SEARCH_H_