tools/gn: remove three unused functions from string_utils.h

tools/gn/string_utils.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef TOOLS_GN_STRING_UTILS_H_
 #define TOOLS_GN_STRING_UTILS_H_
 
 #include "base/strings/string_piece.h"
 
 class Err;
@@ skipping 17 matching lines @@
   return ret;
 }
 
 // Unescapes and expands variables in the given literal, writing the result
 // to the given value. On error, sets |err| and returns false.
 bool ExpandStringLiteral(Scope* scope,
                          const Token& literal,
                          Value* result,
                          Err* err);
 
-// Removes the given prefix from the string. Asserts if the string does
-// not have the given prefix.
-//
-// Note: could potentially return a StringPiece into the str.
-std::string RemovePrefix(const std::string& str, const std::string& prefix);

[tfarina, 2015/12/01 19:53:44]

I found this because I was interested on RemovePrefix and went to look for its
usage and to my surprise discovered there was no more usages :)

-
-// Appends the given string piece to the given string. This avoids an
-// intermediate copy.
-inline void AppendStringPiece(std::string* dest,
-                              const base::StringPiece& piece) {
-  dest->append(piece.data(), piece.size());
-}
-
-// Removes the trailing slash from the given string. This asserts that either
-// the string is empty or it ends with a slash (normally used to process
-// directories).
-void TrimTrailingSlash(std::string* str);
-
 #endif  // TOOLS_GN_STRING_UTILS_H_