Add "bundle_data" target as first step for adding bundle support to gn.

tools/gn/toolchain.cc

Index: tools/gn/toolchain.cc
diff --git a/tools/gn/toolchain.cc b/tools/gn/toolchain.cc
index 2a7035832234fa9da0b3cc61e5120a06f605539d..ee8e7e869ac68c077e1dedce95dd4043ccd869a7 100644
--- a/tools/gn/toolchain.cc
+++ b/tools/gn/toolchain.cc
@@ -151,9 +151,10 @@ Toolchain::ToolType Toolchain::GetToolTypeForTargetFinalOutput(
       return Toolchain::TYPE_ALINK;
     case Target::SOURCE_SET:
       return TYPE_STAMP;
-    case Target::COPY_FILES:
     case Target::ACTION:
     case Target::ACTION_FOREACH:
+    case Target::BUNDLE_DATA:
+    case Target::COPY_FILES:
       return TYPE_STAMP;
     default:
       NOTREACHED();