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

tools/gn/variables.h

Index: tools/gn/variables.h
diff --git a/tools/gn/variables.h b/tools/gn/variables.h
index ee68bd527b1b5358c342b6d9e6c7e04acfb6e608..45fa0ebf9ede90e5eb1b0238a93f0e154f30cb05 100644
--- a/tools/gn/variables.h
+++ b/tools/gn/variables.h
@@ -91,6 +91,22 @@ extern const char kAssertNoDeps[];
 extern const char kAssertNoDeps_HelpShort[];
 extern const char kAssertNoDeps_Help[];
 
+extern const char kBundleRootDir[];
+extern const char kBundleRootDir_HelpShort[];
+extern const char kBundleRootDir_Help[];
+
+extern const char kBundleResourcesDir[];
+extern const char kBundleResourcesDir_HelpShort[];
+extern const char kBundleResourcesDir_Help[];
+
+extern const char kBundleExecutableDir[];
+extern const char kBundleExecutableDir_HelpShort[];
+extern const char kBundleExecutableDir_Help[];
+
+extern const char kBundlePlugInsDir[];
+extern const char kBundlePlugInsDir_HelpShort[];
+extern const char kBundlePlugInsDir_Help[];
+
 extern const char kCflags[];
 extern const char kCflags_HelpShort[];
 extern const char* kCflags_Help;