Move more string_util functions to base namespace.

chrome/common/favicon/fallback_icon_url_parser.cc

Index: chrome/common/favicon/fallback_icon_url_parser.cc
diff --git a/chrome/common/favicon/fallback_icon_url_parser.cc b/chrome/common/favicon/fallback_icon_url_parser.cc
index f91e39f6450d370b81c12160dd4d673306524b99..2f9467b271f7b9003df20953a5c70a88a72d8800 100644
--- a/chrome/common/favicon/fallback_icon_url_parser.cc
+++ b/chrome/common/favicon/fallback_icon_url_parser.cc
@@ -26,9 +26,10 @@ bool IsHexColorString(const std::string& color_str) {
   const size_t* end = kValidHexColorSizes + arraysize(kValidHexColorSizes);
   if (std::find(kValidHexColorSizes, end, len) == end)
     return false;
-  for (auto ch : color_str)
-    if (!IsHexDigit(ch))
+  for (auto ch : color_str) {
+    if (!base::IsHexDigit(ch))
       return false;
+  }
   return true;
 }