[OriginTrials] Support OriginTrialEnabled IDL attribute on constants

third_party/WebKit/LayoutTests/http/tests/origin_trials/resources/origin_trials.js

Index: third_party/WebKit/LayoutTests/http/tests/origin_trials/resources/origin_trials.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/origin_trials/resources/origin_trials.js b/third_party/WebKit/LayoutTests/http/tests/origin_trials/resources/origin_trials.js
index a16f1f2376ca077588589d9ca94deae17efff5c3..a5105dd6bf9de1a2a17772a61cc9e5bbfd997bb3 100644
--- a/third_party/WebKit/LayoutTests/http/tests/origin_trials/resources/origin_trials.js
+++ b/third_party/WebKit/LayoutTests/http/tests/origin_trials/resources/origin_trials.js
@@ -19,9 +19,17 @@ expect_failure = (t) => {
   }, {
     desc: 'Attribute should not exist, with trial disabled',
     code: () => {
+        assert_false('frobulateBindings' in window.internals);
         assert_not_exists(window.internals, 'frobulateBindings');
         assert_equals(window.internals['frobulateBindings'], undefined);
       }
+  }, {
+    desc: 'Constant should not exist, with trial disabled',
+    code: () => {
+        assert_false('FROBULATE_CONST' in window.internals);
+        assert_not_exists(window.internals, 'FROBULATE_CONST');
+        assert_equals(window.internals['FROBULATE_CONST'], undefined);
+      }
   }];
 
   fetch_tests_from_worker(new Worker('resources/disabled-worker.js'));
@@ -47,5 +55,16 @@ test(() => {
     assert_true(window.internals.frobulateBindings, 'Attribute should return boolean value');
   }, 'Attribute should exist and return value');
 
+test(() => {
+    assert_idl_attribute(window.internals, 'FROBULATE_CONST');
+    assert_equals(window.internals.FROBULATE_CONST, 1, 'Constant should return integer value');
+  }, 'Constant should exist and return value');
+
+test(() => {
+    assert_idl_attribute(window.internals, 'FROBULATE_CONST');
+    window.internals.FROBULATE_CONST = 10;
+    assert_equals(window.internals.FROBULATE_CONST, 1, 'Constant should not be modifiable');
+  }, 'Constant should exist and not be modifiable');
+
 fetch_tests_from_worker(new Worker('resources/enabled-worker.js'));
 };