Update Durable Storage API method signature

LayoutTests/http/tests/storage/durability-basics.html

Index: LayoutTests/http/tests/storage/durability-basics.html
diff --git a/LayoutTests/http/tests/storage/durability-basics.html b/LayoutTests/http/tests/storage/durability-basics.html
index b6369ebe4e0ae47737f8f335aceaa8b53d3e3f4c..dc476829a1239f2b9439d19bccfe2acbaef93d98 100644
--- a/LayoutTests/http/tests/storage/durability-basics.html
+++ b/LayoutTests/http/tests/storage/durability-basics.html
@@ -12,11 +12,10 @@ promise_test(function() {
     assert_true(promise instanceof Promise,
         "navigator.storage.requestPersistent() returned a Promise.")
     return promise.then(function (result) {
-        // Layout tests get canned results, not the strings per spec. So testing
+        // Layout tests get canned results, not the value per spec. So testing
         // their values here would only be testing our test plumbing. But we can
-        // test that a string is being returned instead of something else.
-        assert_equals(typeof result, "string", result + " should be a string");
-        assert_greater_than(result.length, 0, "result should have length >0");
+        // test that the type of the returned value is correct.
+        assert_equals(typeof result, "boolean", result + " should be boolean");
     });
 }, "navigator.storage.requestPersistent returns a promise that resolves.");