Make bool type converter descend from BaseTypeConverter.

Bug: 938501
Change-Id: Ia852579e7e600d08c704b67d4dfdd84ea14db5fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625969
Commit-Queue: Allen Bauer <kylixrd@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Auto-Submit: Allen Bauer <kylixrd@chromium.org>
Reviewed-by: Wei Li <weili@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842813}

ui/views/metadata/type_conversion.h

@@ -163,9 +163,7 @@ DECLARE_CONVERSIONS(gfx::Insets)
 #undef DECLARE_CONVERSIONS
 
 template <>
-struct VIEWS_EXPORT TypeConverter<bool> {
-  static constexpr bool is_serializable = true;
-  static bool IsSerializable() { return is_serializable; }
+struct VIEWS_EXPORT TypeConverter<bool> : BaseTypeConverter<true> {
   static base::string16 ToString(bool source_value);
   static base::Optional<bool> FromString(const base::string16& source_value);
   static ValidStrings GetValidStrings();