Move more string_util functions to base namespace.

net/tools/dump_cache/url_to_filename_encoder.cc

Index: net/tools/dump_cache/url_to_filename_encoder.cc
diff --git a/net/tools/dump_cache/url_to_filename_encoder.cc b/net/tools/dump_cache/url_to_filename_encoder.cc
index b807ec092671b01671277fd1986f97a75d4c7797..083b9c546a9d100726b0e659ad076f8526fa5fd7 100644
--- a/net/tools/dump_cache/url_to_filename_encoder.cc
+++ b/net/tools/dump_cache/url_to_filename_encoder.cc
@@ -18,7 +18,7 @@ namespace {
 // The function checks for '\0' for string termination.
 int HexDigitsPrefix(const char* buf, int num_digits) {
   for (int i = 0; i < num_digits; i++) {
-    if (!IsHexDigit(buf[i]))
+    if (!base::IsHexDigit(buf[i]))
       return 0;  // This also detects end of string as '\0' is not xdigit.
   }
   return 1;