Make HasAuthorBackground/Border monotonic_flags

They are currently monotonic flags in practice (for a reason [1]), but
not actually generated as such. This is because the same flags were
set in a non-monotonic way in the old code path in the StyleResolver.

[1] https://crrev.com/1af5ee6fdf9ae9a96911385b8ea634cfdef8a7be

Change-Id: I4ea461b1e7e024ccbc98a26bdfa7982a107609ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321411Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Anders Hartvoll Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792596}

third_party/blink/renderer/core/css/resolver/style_cascade.cc

@@ -165,9 +165,9 @@ void StyleCascade::Apply(CascadeFilter filter) {
 
   if (state_.Style()->HasAppearance()) {
     if (resolver.AuthorFlags() & CSSProperty::kBackground)
-      state_.Style()->SetHasAuthorBackground(true);
+      state_.Style()->SetHasAuthorBackground();
     if (resolver.AuthorFlags() & CSSProperty::kBorder)
-      state_.Style()->SetHasAuthorBorder(true);
+      state_.Style()->SetHasAuthorBorder();
   }
 }
 

third_party/blink/renderer/core/style/computed_style_extra_fields.json5

@@ -681,16 +681,12 @@
     // Style adjustment for appearance is disabled when certain properties are set.
     {
       name: "HasAuthorBackground",
-      field_template: "primitive",
-      type_name: "bool",
-      field_group: "*",
+      field_template: "monotonic_flag",
       default_value: "false",
     },
     {
       name: "HasAuthorBorder",
-      field_template: "primitive",
-      type_name: "bool",
-      field_group: "*",
+      field_template: "monotonic_flag",
       default_value: "false",
     },
     {