Use ICU case conversion/transliterator for case conversion behind a flag

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 8621 matching lines @@
   };
 
   // Representation of the flat content of a String.
   // A non-flat string doesn't have flat content.
   // A flat string has content that's encoded as a sequence of either
   // one-byte chars or two-byte UC16.
   // Returned by String::GetFlatContent().
   class FlatContent {
    public:
     // Returns true if the string is flat and this structure contains content.
-    bool IsFlat() { return state_ != NON_FLAT; }
+    bool IsFlat() const { return state_ != NON_FLAT; }
     // Returns true if the structure contains one-byte content.
-    bool IsOneByte() { return state_ == ONE_BYTE; }
+    bool IsOneByte() const { return state_ == ONE_BYTE; }
     // Returns true if the structure contains two-byte content.
-    bool IsTwoByte() { return state_ == TWO_BYTE; }
+    bool IsTwoByte() const { return state_ == TWO_BYTE; }
 
     // Return the one byte content of the string. Only use if IsOneByte()
     // returns true.
-    Vector<const uint8_t> ToOneByteVector() {
+    Vector<const uint8_t> ToOneByteVector() const {
       DCHECK_EQ(ONE_BYTE, state_);
       return Vector<const uint8_t>(onebyte_start, length_);
     }
     // Return the two-byte content of the string. Only use if IsTwoByte()
     // returns true.
-    Vector<const uc16> ToUC16Vector() {
+    Vector<const uc16> ToUC16Vector() const {
       DCHECK_EQ(TWO_BYTE, state_);
       return Vector<const uc16>(twobyte_start, length_);
     }
 
-    uc16 Get(int i) {
+    uc16 Get(int i) const {
       DCHECK(i < length_);
       DCHECK(state_ != NON_FLAT);
       if (state_ == ONE_BYTE) return onebyte_start[i];
       return twobyte_start[i];
     }
 
     bool UsesSameString(const FlatContent& other) const {
       return onebyte_start == other.onebyte_start;
     }
 
@@ skipping 2055 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_