Enable incremental marking when --expose-gc is turned on.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 8b033d60afb1af728db37b2bb7808a311d1fe151..26afb4d403a541788b93bc71650ecbe72a4133ab 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -5603,11 +5603,11 @@ bool Heap::IdleNotification(int hint) {
   if (contexts_disposed_ > 0) {
     contexts_disposed_ = 0;
     int mark_sweep_time = Min(TimeMarkSweepWouldTakeInMs(), 1000);
-    if (hint >= mark_sweep_time && !FLAG_expose_gc &&
-        incremental_marking()->IsStopped()) {
+    if (hint >= mark_sweep_time) {
       HistogramTimerScope scope(isolate_->counters()->gc_context());
-      CollectAllGarbage(kReduceMemoryFootprintMask,
-                        "idle notification: contexts disposed");
+      CollectAllGarbage(
+          kReduceMemoryFootprintMask | kAbortIncrementalMarkingMask,

[Michael Starzinger, 2014/01/20 14:09:30]

This not only removes the special handling of --expose-gc but also changes
semantics of IdleNotification. I have no beef with this change in particular,
but maybe we should do that in a separate CL, so that --noexpose-gc semantics
stay unchanged with this CL.

[Hannes Payer (out of office), 2014/01/20 14:28:42]

Done, makes sense. I will do that.

+          "idle notification: contexts disposed");
     } else {
       AdvanceIdleIncrementalMarking(step_size);
     }
@@ -5619,7 +5619,7 @@ bool Heap::IdleNotification(int hint) {
     return false;
   }
 
-  if (!FLAG_incremental_marking || FLAG_expose_gc || Serializer::enabled()) {
+  if (!FLAG_incremental_marking || Serializer::enabled()) {
     return IdleGlobalGC();
   }