Pull in ASCII<->UTF16 from Chromium

base/strings/string_util.h

Index: base/strings/string_util.h
diff --git a/base/strings/string_util.h b/base/strings/string_util.h
index 51ebba39e536064d10780889ab85a16dc7c80c43..f40a8ace2a70288d51040d070fb4c23ca097a5fc 100644
--- a/base/strings/string_util.h
+++ b/base/strings/string_util.h
@@ -7,12 +7,16 @@
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
+#include "base/strings/string_piece.h"
 
 namespace base {
 
 int vsnprintf(char* buffer, size_t size, const char* format, va_list arguments)
     PRINTF_FORMAT(3, 0);
 
+bool IsStringASCII(const StringPiece& str);
+bool IsStringASCII(const StringPiece16& str);
+
 }  // namespace base
 
 #if defined(OS_WIN)