Revert "Extract common code from StringPiece and StringPiece16 into a templated base class....

base/utf_offset_string_conversions.h

Index: base/utf_offset_string_conversions.h
diff --git a/base/utf_offset_string_conversions.h b/base/utf_offset_string_conversions.h
index 97b641edda8b49a9a9797ec4cd08966f2400c277..c2faf3a491599cf33648d06380fd8525876d7868 100644
--- a/base/utf_offset_string_conversions.h
+++ b/base/utf_offset_string_conversions.h
@@ -11,7 +11,11 @@
 
 #include "base/base_export.h"
 #include "base/string16.h"
-#include "base/string_piece.h"
+
+namespace base {
+class StringPiece;
+class StringPiece16;
+}
 
 // Like the conversions in utf_string_conversions.h, but also takes one or more
 // offsets (|offset[s]_for_adjustment|) into the source strings, each offset