Add support for Mac/iOS application bundles to GN tool.

tools/gn/variables.cc

Index: tools/gn/variables.cc
diff --git a/tools/gn/variables.cc b/tools/gn/variables.cc
index a835b22d6b2c6fa5db7dd999dd9a3730e4070550..97777486169aa22a545c6c9afad5b99065e4b4a2 100644
--- a/tools/gn/variables.cc
+++ b/tools/gn/variables.cc
@@ -391,6 +391,17 @@ const char kArgs_Help[] =
     "\n"
     "  See also \"gn help action\" and \"gn help action_foreach\".\n";
 
+const char kBundleData[] = "bundle_data";
+const char kBundleData_HelpShort[] =
+    "bundle_data: [file list] Runtime data dependency (Mac/iOS).";
+const char kBundleData_Help[] =
+    "bundle_data: Runtime data dependency (Mac/iOS).\n"
+    "\n"
+    "  List files that are required at runtime by the current target and\n"
+    "  should be copied into the application bundle.\n"
+    "\n"
+    "  See also \"gn help copy_bundle_data\".\n";
+
 const char kCflags[] = "cflags";
 const char kCflags_HelpShort[] =
     "cflags: [string list] Flags passed to all C compiler variants.";