[regexp] use C++ API for unicode set over C API.

src/regexp/jsregexp.cc

Index: src/regexp/jsregexp.cc
diff --git a/src/regexp/jsregexp.cc b/src/regexp/jsregexp.cc
index 441c76b95d4fc5419f68b9d1c954a71f77146d1d..9e1941fc0a9e70414129822316abbe8e79d5fdbe 100644
--- a/src/regexp/jsregexp.cc
+++ b/src/regexp/jsregexp.cc
@@ -27,7 +27,7 @@
 #include "src/unicode-decoder.h"
 
 #ifdef V8_I18N_SUPPORT
-#include "unicode/uset.h"
+#include "unicode/uniset.h"
 #include "unicode/utypes.h"
 #endif  // V8_I18N_SUPPORT
 
@@ -5114,30 +5114,22 @@ void AddUnicodeCaseEquivalents(RegExpCompiler* compiler,
   // Use ICU to compute the case fold closure over the ranges.
   DCHECK(compiler->unicode());
   DCHECK(compiler->ignore_case());
-  USet* set = uset_openEmpty();
+  icu::UnicodeSet set;
   for (int i = 0; i < ranges->length(); i++) {
-    uset_addRange(set, ranges->at(i).from(), ranges->at(i).to());
+    set.add(ranges->at(i).from(), ranges->at(i).to());
   }
   ranges->Clear();
-  uset_closeOver(set, USET_CASE_INSENSITIVE);
+  set.closeOver(USET_CASE_INSENSITIVE);
   // Full case mapping map single characters to multiple characters.
   // Those are represented as strings in the set. Remove them so that
   // we end up with only simple and common case mappings.
-  uset_removeAllStrings(set);
-  int item_count = uset_getItemCount(set);
-  int item_result = 0;
-  UErrorCode ec = U_ZERO_ERROR;
+  set.removeAllStrings();
   Zone* zone = compiler->zone();
-  for (int i = 0; i < item_count; i++) {
-    uc32 start = 0;
-    uc32 end = 0;
-    item_result += uset_getItem(set, i, &start, &end, nullptr, 0, &ec);
-    ranges->Add(CharacterRange::Range(start, end), zone);
+  for (int i = 0; i < set.getRangeCount(); i++) {
+    ranges->Add(CharacterRange::Range(set.getRangeStart(i), set.getRangeEnd(i)),
+                zone);
   }
   // No errors and everything we collected have been ranges.
-  DCHECK_EQ(U_ZERO_ERROR, ec);
-  DCHECK_EQ(0, item_result);
-  uset_close(set);
 #else
   // Fallback if ICU is not included.
   CharacterRange::AddCaseEquivalents(compiler->isolate(), compiler->zone(),