Support more configurability in GN toolchains

tools/gn/escape_unittest.cc

 // 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.
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/escape.h"
 
 TEST(Escape, Ninja) {
   EscapeOptions opts;
   opts.mode = ESCAPE_NINJA;
@@ skipping 32 matching lines @@
   EscapeOptions opts;
   opts.mode = ESCAPE_NINJA_COMMAND;
   opts.platform = ESCAPE_PLATFORM_POSIX;
 
   // : and $ ninja escaped with $. Then Shell-escape backslashes and quotes.
   EXPECT_EQ("a$:\\$ \\\"\\$$\\\\b", EscapeString("a: \"$\\b", opts, NULL));
 
   // Some more generic shell chars.
   EXPECT_EQ("a_\\;\\<\\*b", EscapeString("a_;<*b", opts, NULL));
 }
+
+TEST(Escape, NinjaPreformatted) {
+  EscapeOptions opts;
+  opts.mode = ESCAPE_NINJA_PREFORMATTED_COMMAND;
+
+  // Only $ is escaped.
+  EXPECT_EQ("a: \"$$\\b<;", EscapeString("a: \"$\\b<;", opts, NULL));
+}