Add more string_util functions to base namespace.

net/base/filename_util_internal.cc

Index: net/base/filename_util_internal.cc
diff --git a/net/base/filename_util_internal.cc b/net/base/filename_util_internal.cc
index 8d7509f3ce6187cc266a2198e91247acd0d3e8b1..96376aed6fc764ad2a28213a539d13856e4d632b 100644
--- a/net/base/filename_util_internal.cc
+++ b/net/base/filename_util_internal.cc
@@ -41,8 +41,10 @@ void SanitizeGeneratedFileName(base::FilePath::StringType* filename,
   if (filename->empty())
     return;
   // Replace any path information by changing path separators.
-  ReplaceSubstringsAfterOffset(filename, 0, FILE_PATH_LITERAL("/"), kReplace);
-  ReplaceSubstringsAfterOffset(filename, 0, FILE_PATH_LITERAL("\\"), kReplace);
+  base::ReplaceSubstringsAfterOffset(
+      filename, 0, FILE_PATH_LITERAL("/"), kReplace);
+  base::ReplaceSubstringsAfterOffset(
+      filename, 0, FILE_PATH_LITERAL("\\"), kReplace);
 }
 
 // Returns the filename determined from the last component of the path portion