Mojo: Support enums as map keys in WTF

mojo/public/tools/bindings/generators/cpp_templates/enum_macros.tmpl

Index: mojo/public/tools/bindings/generators/cpp_templates/enum_macros.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/enum_macros.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/enum_macros.tmpl
index 9400ca77041e65cf319e0512101d619d4b63ecb6..92073bc5d5973e07791753c57e3de40799b4e286 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/enum_macros.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/enum_macros.tmpl
@@ -78,3 +78,50 @@ template <>
 struct hash<{{enum_name}}>
     : public mojo::internal::EnumHashImpl<{{enum_name}}> {};
 {%- endmacro %}
+
+{%- macro enum_hash_blink(enum) %}
+{%-   set enum_name = enum|get_qualified_name_for_kind(
+          flatten_nested_kind=True, include_variant=False) %}
+{%-   set hash_fn_name = enum|wtf_hash_fn_name_for_enum %}
+{#    We need two unused enum values: #}
+{%-   set empty_value = -1000000 %}
+{%-   set deleted_value = -1000001 %}
+{%-   set empty_value_unused = "false" if empty_value in enum|all_enum_values else "true" %}
+{%-   set deleted_value_unused = "false" if empty_value in enum|all_enum_values else "true" %}
+namespace WTF {
+struct {{hash_fn_name}} {
+  static unsigned hash(const {{enum_name}}& value) {
+    typedef base::underlying_type<{{enum_name}}>::type utype;
+    return DefaultHash<utype>::Hash().hash(static_cast<utype>(value));
+  }
+  static bool equal(const {{enum_name}}& left, const {{enum_name}}& right) {
+    return left == right;
+  }
+  static const bool safeToCompareToEmptyOrDeleted = true;
+};
+
+template <>
+struct DefaultHash<{{enum_name}}> {
+  using Hash = {{hash_fn_name}};
+};
+
+template <>
+struct HashTraits<{{enum_name}}>
+    : public GenericHashTraits<{{enum_name}}> {
+  static_assert({{empty_value_unused}},
+                "{{empty_value}} is a reserved enum value");
+  static_assert({{deleted_value_unused}},
+                "{{deleted_value}} is a reserved enum value");
+  static const bool hasIsEmptyValueFunction = true;
+  static bool isEmptyValue(const {{enum_name}}& value) {
+    return value == static_cast<{{enum_name}}>({{empty_value}});
+  }
+  static void constructDeletedValue({{enum_name}}& slot, bool) {
+    slot = static_cast<{{enum_name}}>({{deleted_value}});
+  }
+  static bool isDeletedValue(const {{enum_name}}& value) {
+    return value == static_cast<{{enum_name}}>({{deleted_value}});
+  }
+};
+}  // namespace WTF
+{%- endmacro %}