Optimize phishing page term feature extraction.

base/i18n/case_conversion.cc

Index: base/i18n/case_conversion.cc
diff --git a/base/i18n/case_conversion.cc b/base/i18n/case_conversion.cc
index 4aa90286a42519105d28608425705f620bb55ff5..8dbae509a7d714ac49d311685355f02dbc0cff9f 100644
--- a/base/i18n/case_conversion.cc
+++ b/base/i18n/case_conversion.cc
@@ -9,14 +9,14 @@
 namespace base {
 namespace i18n {
 
-string16 ToLower(const string16& string) {
-  icu::UnicodeString unicode_string(string.c_str(), string.size());
+string16 ToLower(const WideStringPiece& string) {
+  icu::UnicodeString unicode_string(string.data(), string.size());
   unicode_string.toLower();
   return string16(unicode_string.getBuffer(), unicode_string.length());
 }
 
-string16 ToUpper(const string16& string) {
-  icu::UnicodeString unicode_string(string.c_str(), string.size());
+string16 ToUpper(const WideStringPiece& string) {
+  icu::UnicodeString unicode_string(string.data(), string.size());
   unicode_string.toUpper();
   return string16(unicode_string.getBuffer(), unicode_string.length());
 }