Make ScriptPromiseResolver RefCountedWillBeRefCountedGarbageCollected.

LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html

Index: LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
diff --git a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
index 2328448d4e8d4de8f508684bff120a7adb456b88..54f2e87fc7657c3a696ac416302343e52e91d9ac 100644
--- a/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
+++ b/LayoutTests/media/encrypted-media/encrypted-media-lifetime-mediakeysession-reference.html
@@ -39,7 +39,13 @@
                     assert_equals(typeof mediaKeys.createSession, 'function');
 
                     // 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()');
 
                     // Create 3 sessions.
                     mediaKeySession1 = mediaKeys.createSession();
@@ -47,19 +53,23 @@
                 }).then(function() {
                     assert_true(mediaKeySession1.sessionId && mediaKeySession1.sessionId.length > 0);
                     // Should be 1 MediaKeySession.
-                    assert_equals(numActiveDOMObjectsCreated(), 1, 'mediaKeys.createSession(1)');
+                    // numActiveDOMObjectsCreated() <= 4 (1 is a ScriptPromiseResolver owned by
+                    // ContentDecryptionModuleResultPromise and the other is MediaKeySession).
+                    assert_less_than_equal(numActiveDOMObjectsCreated(), 4, 'MediaKeys.createSession(1)');
                     mediaKeySession2 = mediaKeys.createSession();
                     return mediaKeySession2.generateRequest(initDataType, initData);
                 }).then(function() {
                     assert_true(mediaKeySession2.sessionId && mediaKeySession2.sessionId.length > 0);
                     // Should be 2 MediaKeySessions.
-                    assert_equals(numActiveDOMObjectsCreated(), 2, 'mediaKeys.createSession(2)');
+                    // numActiveDOMObjectsCreated() <= 6 (ditto)
+                    assert_less_than_equal(numActiveDOMObjectsCreated(), 6, 'mediaKeys.createSession(2)');
                     mediaKeySession3 = mediaKeys.createSession();
                     return mediaKeySession3.generateRequest(initDataType, initData);
                 }).then(function() {
                     assert_true(mediaKeySession3.sessionId && mediaKeySession3.sessionId.length > 0);
                     // Should be 3 MediaKeySessions.
-                    assert_equals(numActiveDOMObjectsCreated(), 3, 'mediaKeys.createSession(3)');
+                    // numActiveDOMObjectsCreated() <= 8 (ditto)
+                    assert_less_than_equal(numActiveDOMObjectsCreated(), 8, 'mediaKeys.createSession(3)');
 
                     // Run gc(). All sessions should remain as we have a
                     // reference to each one. However, running gc()