Add "create_bundle" target in order to support bundle with gn.

tools/gn/bundle_file_rule.h

Index: tools/gn/bundle_file_rule.h
diff --git a/tools/gn/bundle_file_rule.h b/tools/gn/bundle_file_rule.h
new file mode 100644
index 0000000000000000000000000000000000000000..e1b410af701e7cd05ca48e3a7f41ca2731e66a7a
--- /dev/null
+++ b/tools/gn/bundle_file_rule.h
@@ -0,0 +1,42 @@
+// Copyright 2016 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_BUNDLE_FILE_RULE_H_
+#define TOOLS_GN_BUNDLE_FILE_RULE_H_
+
+#include <vector>
+
+#include "tools/gn/source_file.h"
+#include "tools/gn/substitution_pattern.h"
+
+class BundleData;
+class Settings;
+class SourceFile;
+class OutputFile;
+
+class BundleFileRule {
+ public:
+  BundleFileRule(const std::vector<SourceFile> sources,
+                 const SubstitutionPattern& pattern);
+  ~BundleFileRule();
+
+  SourceFile ApplyPatternToSource(
+      const Settings* settings,
+      const BundleData& bundle_data,
+      const SourceFile& source_file) const;
+
+  OutputFile ApplyPatternToSourceAsOutputFile(
+      const Settings* settings,
+      const BundleData& bundle_data,
+      const SourceFile& source_file) const;
+
+  const std::vector<SourceFile>& sources() const { return sources_; }
+  const SubstitutionPattern& pattern() const { return pattern_; }
+
+ private:
+  std::vector<SourceFile> sources_;
+  SubstitutionPattern pattern_;
+};
+
+#endif  // TOOLS_GN_BUNDLE_FILE_RULE_H_