Do nothing when sweeping is in progress.

test/unittests/heap/gc-idle-time-handler-unittest.cc

Index: test/unittests/heap/gc-idle-time-handler-unittest.cc
diff --git a/test/unittests/heap/gc-idle-time-handler-unittest.cc b/test/unittests/heap/gc-idle-time-handler-unittest.cc
index 66b022c36020519be27d9a8993bf521b3da86fb6..7d17e2bc20e7baea07d7063bb8f07d6ab754d846 100644
--- a/test/unittests/heap/gc-idle-time-handler-unittest.cc
+++ b/test/unittests/heap/gc-idle-time-handler-unittest.cc
@@ -328,6 +328,18 @@ TEST_F(GCIdleTimeHandlerTest, CannotFinalizeSweeping) {
 }
 
 
+TEST_F(GCIdleTimeHandlerTest, NoIncrementalMarkingWhileSweeping) {
+  GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
+  heap_state.incremental_marking_stopped = false;
+  heap_state.can_start_incremental_marking = false;
+  heap_state.sweeping_in_progress = true;
+  heap_state.sweeping_completed = false;
+  double idle_time_ms = 10.0;
+  GCIdleTimeAction action = handler()->Compute(idle_time_ms, heap_state);
+  EXPECT_EQ(DO_NOTHING, action.type);
+}
+
+
 TEST_F(GCIdleTimeHandlerTest, StopEventually1) {
   GCIdleTimeHandler::HeapState heap_state = DefaultHeapState();
   heap_state.incremental_marking_stopped = true;