Support more configurability in GN toolchains

tools/gn/escape_unittest.cc

Index: tools/gn/escape_unittest.cc
diff --git a/tools/gn/escape_unittest.cc b/tools/gn/escape_unittest.cc
index 1a79a78b671c531ce646e6532e0b0a75b7a03518..fd4934861e4b84997bb0390de4cd70e02a3c8abe 100644
--- a/tools/gn/escape_unittest.cc
+++ b/tools/gn/escape_unittest.cc
@@ -50,3 +50,11 @@ TEST(Escape, PosixCommand) {
   // 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));
+}