Move more string_util functions to base namespace.

components/translate/core/language_detection/language_detection_util.cc

Index: components/translate/core/language_detection/language_detection_util.cc
diff --git a/components/translate/core/language_detection/language_detection_util.cc b/components/translate/core/language_detection/language_detection_util.cc
index 9556bb9351a9543ea0467b7dd2a539877957a922..144071422ce254bed984b521a896dd2123a0ebc8 100644
--- a/components/translate/core/language_detection/language_detection_util.cc
+++ b/components/translate/core/language_detection/language_detection_util.cc
@@ -324,7 +324,7 @@ bool IsValidLanguageCode(const std::string& code) {
 
   for (std::string::const_iterator it = main_code.begin();
        it != main_code.end(); ++it) {
-    if (!IsAsciiAlpha(*it))
+    if (!base::IsAsciiAlpha(*it))
       return false;
   }
 
@@ -338,7 +338,7 @@ bool IsValidLanguageCode(const std::string& code) {
 
   for (std::string::const_iterator it = sub_code.begin();
        it != sub_code.end(); ++it) {
-    if (!IsAsciiAlpha(*it))
+    if (!base::IsAsciiAlpha(*it))
       return false;
   }