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

tools/gn/bundle_file_rule.cc

Index: tools/gn/bundle_file_rule.cc
diff --git a/tools/gn/bundle_file_rule.cc b/tools/gn/bundle_file_rule.cc
new file mode 100644
index 0000000000000000000000000000000000000000..76d848e8cd4617cda03113780267a3ff05ce07e6
--- /dev/null
+++ b/tools/gn/bundle_file_rule.cc
@@ -0,0 +1,58 @@
+// 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.
+
+#include "tools/gn/bundle_file_rule.h"
+
+#include "tools/gn/output_file.h"
+#include "tools/gn/settings.h"
+#include "tools/gn/substitution_pattern.h"
+#include "tools/gn/substitution_writer.h"
+#include "tools/gn/target.h"
+
+BundleFileRule::BundleFileRule(const std::vector<SourceFile> sources,
+                               const SubstitutionPattern& pattern)
+    : sources_(sources), pattern_(pattern) {}
+
+BundleFileRule::~BundleFileRule() {}
+
+SourceFile BundleFileRule::ApplyPatternToSource(
+    const Settings* settings,
+    const BundleData& bundle_data,
+    const SourceFile& source_file) const {
+  std::string output_path;
+  for (const auto& subrange : pattern_.ranges()) {
+     switch (subrange.type) {
+       case SUBSTITUTION_LITERAL:
+         output_path.append(subrange.literal);
+         break;
+       case SUBSTITUTION_BUNDLE_ROOT_DIR:
+         output_path.append(bundle_data.root_dir());
+         break;
+       case SUBSTITUTION_BUNDLE_RESOURCES_DIR:
+         output_path.append(bundle_data.resources_dir());
+         break;
+       case SUBSTITUTION_BUNDLE_EXECUTABLE_DIR:
+         output_path.append(bundle_data.executable_dir());
+         break;
+       case SUBSTITUTION_BUNDLE_PLUGINS_DIR:
+         output_path.append(bundle_data.plugins_dir());
+         break;
+       default:
+         output_path.append(
+             SubstitutionWriter::GetSourceSubstitution(
+                 settings, source_file, subrange.type,
+                 SubstitutionWriter::OUTPUT_ABSOLUTE, SourceDir()));
+         break;
+     }
+  }
+  return SourceFile(SourceFile::SWAP_IN, &output_path);
+}
+
+OutputFile BundleFileRule::ApplyPatternToSourceAsOutputFile(
+    const Settings* settings,
+    const BundleData& bundle_data,
+    const SourceFile& source_file) const {
+  return OutputFile(settings->build_settings(),
+                    ApplyPatternToSource(settings, bundle_data, source_file));
+}