Separate out some more ICU from base and into base/i18n....

base/string_util.h

Index: base/string_util.h
===================================================================
--- base/string_util.h	(revision 28219)
+++ base/string_util.h	(working copy)
@@ -140,8 +140,6 @@
 // The non-wide version has two functions:
 // * TrimWhitespaceASCII()
 //   This function is for ASCII strings and only looks for ASCII whitespace;
-// * TrimWhitespaceUTF8()
-//   This function is for UTF-8 strings and looks for Unicode whitespace.
 // Please choose the best one according to your usage.
 // NOTE: Safe to use the same variable for both input and output.
 enum TrimPositions {
@@ -156,9 +154,6 @@
 TrimPositions TrimWhitespaceASCII(const std::string& input,
                                   TrimPositions positions,
                                   std::string* output);
-TrimPositions TrimWhitespaceUTF8(const std::string& input,
-                                 TrimPositions positions,
-                                 std::string* output);
 
 // Deprecated. This function is only for backward compatibility and calls
 // TrimWhitespaceASCII().