Add initial prototype for the GN meta-buildsystem.

tools/gn/escape.h

Index: tools/gn/escape.h
diff --git a/tools/gn/escape.h b/tools/gn/escape.h
new file mode 100644
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+++ b/tools/gn/escape.h
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+// 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_ESCAPE_H_
+#define TOOLS_GN_ESCAPE_H_
+
+#include <iosfwd>
+
+#include "base/strings/string_piece.h"
+
+// TODO(brettw) we may need to make this a bitfield. If we want to write a
+// shell command in a ninja file, we need the shell characters to be escaped,
+// and THEN the ninja characters. Or maybe we require the caller to do two
+// passes.
+enum EscapingMode {
+  ESCAPE_NONE,   // No escaping.
+  ESCAPE_NINJA,  // Ninja string escaping.
+  ESCAPE_SHELL,  // Shell string escaping.
+};
+
+struct EscapeOptions {
+  EscapeOptions()
+      : mode(ESCAPE_NONE),
+        convert_slashes(false),
+        inhibit_quoting(false) {
+  }
+
+  EscapingMode mode;
+
+  // When set, converts forward-slashes to system-specific path separators.
+  bool convert_slashes;
+
+  // When the escaping mode is ESCAPE_SHELL, the escaper will normally put
+  // quotes around things with spaces. If this value is set to true, we'll
+  // disable the quoting feature and just add the spaces.
+  //
+  // This mode is for when quoting is done at some higher-level. Defaults to
+  // false.
+  bool inhibit_quoting;
+};
+
+// Escapes the given input, returnining the result.
+std::string EscapeString(const base::StringPiece& str,
+                         const EscapeOptions& options);
+
+// Same as EscapeString but writes the results to the given stream, saving a
+// copy.
+void EscapeStringToStream(std::ostream& out,
+                          const base::StringPiece& str,
+                          const EscapeOptions& options);
+
+#endif  // TOOLS_GN_ESCAPE_H_