Revert of clang plugin: Remove check-templates toggle.

tools/clang/plugins/Options.h

Index: tools/clang/plugins/Options.h
diff --git a/tools/clang/plugins/Options.h b/tools/clang/plugins/Options.h
index de82007afab4e12c7088a3f48251631e73102575..5e854fd1e4f33da353dc88c1f8ea16d6b97932df 100644
--- a/tools/clang/plugins/Options.h
+++ b/tools/clang/plugins/Options.h
@@ -12,6 +12,7 @@
   bool enforce_in_pdf = false;
   bool enforce_in_thirdparty_webkit = false;  // Use in Blink code itself
   bool check_enum_last_value = false;
+  bool check_templates = false;
   // This is needed for some distributed build-sytems to respect banned
   // paths. See https://crbug.com/583454 for details.
   bool no_realpath = false;