Update ToLower/UpperASCII API

base/environment.cc

Index: base/environment.cc
diff --git a/base/environment.cc b/base/environment.cc
index 245051d0c1840688552d1fa453356be8e20cc236..11b2bc39a9e0600741fb55559ca609c44da3641a 100644
--- a/base/environment.cc
+++ b/base/environment.cc
@@ -33,9 +33,9 @@ class EnvironmentImpl : public Environment {
     char first_char = variable_name[0];
     std::string alternate_case_var;
     if (first_char >= 'a' && first_char <= 'z')
-      alternate_case_var = StringToUpperASCII(std::string(variable_name));
+      alternate_case_var = ToUpperASCII(variable_name);
     else if (first_char >= 'A' && first_char <= 'Z')
-      alternate_case_var = StringToLowerASCII(std::string(variable_name));
+      alternate_case_var = ToLowerASCII(variable_name);
     else
       return false;
     return GetVarImpl(alternate_case_var.c_str(), result);