Add @abstract to allowed Closure linter tags

third_party/closure_compiler/closure_args.gni

Index: third_party/closure_compiler/closure_args.gni
diff --git a/third_party/closure_compiler/closure_args.gni b/third_party/closure_compiler/closure_args.gni
index 51f24efa1e69cb4ed2104fa63e9cb948b56f24fc..b1cd18974247bb1e587e661eecd99c629468a76d 100644
--- a/third_party/closure_compiler/closure_args.gni
+++ b/third_party/closure_compiler/closure_args.gni
@@ -5,6 +5,7 @@
 # GYP version: third_party/closure_compiler/closure_args.gypi
 closure_args = [
   "compilation_level=SIMPLE_OPTIMIZATIONS",
+
   "extra_annotation_name=attribute",
   "extra_annotation_name=demo",
   "extra_annotation_name=element",
@@ -13,6 +14,7 @@ closure_args = [
   "extra_annotation_name=homepage",
   "extra_annotation_name=status",
   "extra_annotation_name=submodule",
+
   "jscomp_error=accessControls",
   "jscomp_error=ambiguousFunctionDecl",
   "jscomp_error=checkTypes",
@@ -31,9 +33,12 @@ closure_args = [
   "jscomp_error=unknownDefines",
   "jscomp_error=uselessCode",
   "jscomp_error=visibility",
+
   "language_in=ECMASCRIPT6_STRICT",
   "language_out=ECMASCRIPT5_STRICT",
+
   "polymer_pass",
+
   "source_map_format=V3",
 ]