Make ScriptPromiseResolver RefCountedWillBeRefCountedGarbageCollected.

LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeys-with-session.html

Index: LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeys-with-session.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeys-with-session.html b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeys-with-session.html
index 6ab4bb750278a08e25315d23933c23ff59bee585..565f20e39f16a0c1be80a166c594febbfe5142b4 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeys-with-session.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeys-with-session.html
@@ -42,17 +42,28 @@
                     mediaKeys = result;
 
                     // Verify MediaKeys are not an ActiveDOMObject.
-                    assert_equals(numActiveDOMObjectsCreated(), 0, 'MediaKeys.create()');
+                    // MediaKeys are not an ActiveDOMObject, but when creating MediaKeys,
+                    // creating ScriptPromiseResolvers, which are ActiveDOMObjects.
+                    // so numActiveDOMObjetsCreated() <= 2 (1 is MediaKeysInitializer and
+                    // the other is MediaKeySystemAccessInitializer).
+                    // When enabling oilpan, the ScriptPromiseResolvers are not destroyed
+                    // immediately. So numActiveDOMObjectsCreate() <= 2.
+                    assert_less_than_equal(numActiveDOMObjectsCreated(), 2, 'MediaKeys.create()');
 
                     var initDataType = getInitDataType();
                     var mediaKeySession = mediaKeys.createSession();
                     return mediaKeySession.generateRequest(initDataType, getInitData(initDataType));
                 }).then(function() {
                     // 1 MediaKeySession.
-                    assert_equals(numActiveDOMObjectsCreated(), 1, 'MediaKeys.createSession()');
+                    // numActiveDOMObjectsCreated() <= 4 (1 is a ScriptPromiseResolver owned by
+                    // ContentDecryptionModuleResultPromise and the other is MediaKeySession).
+                    assert_less_than_equal(numActiveDOMObjectsCreated(), 4, 'MediaKeys.createSession(1)');
 
                     // Run gc(), should not affect MediaKeys object nor the
                     // session since we still have a reference to it.
+
+                    // When enabling oilpan GC, the in-active ScriptPromiseResolvers will be
+                    // destroyed.
                     return createGCPromise();
                 }).then(function(result) {
                     assert_equals(typeof mediaKeys.createSession, 'function');