Fix idle notification for background tab.

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index f4d346330671b4a5ece30a15af2780ceb8db1d83..376d0d89a5c54ce463bdec570655e02368223855 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -15434,6 +15434,9 @@ TEST(TestIdleNotification) {
         (v8::base::TimeTicks::HighResolutionNow().ToInternalValue() /
          static_cast<double>(v8::base::Time::kMicrosecondsPerSecond)) +
         IdlePauseInSeconds);
+    if (CcTest::heap()->mark_compact_collector()->sweeping_in_progress()) {
+      CcTest::heap()->mark_compact_collector()->EnsureSweepingCompleted();
+    }
   }
   intptr_t final_size = CcTest::heap()->SizeOfObjects();
   CHECK(finished);