Add filler at the new space top when forcing scavenge.

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index c7f363821fcb25ea226bbaa8f6456078ed8551a5..42e56ca1eb9e2bb40498d9ea2d341c71a67f6b4e 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -773,6 +773,21 @@ void Heap::CollectAllAvailableGarbage(const char* gc_reason) {
 }
 
 
+void Heap::EnsureFillerObjectAtTop() {
+  // There may be an allocation memento behind every object in new space.
+  // If we evacuate a not full new space or if we are on the last page of
+  // the new space, then there may be uninitialized memory behind the top
+  // pointer of the new space page. We store a filler object there to
+  // identify the unused space.
+  Address from_top = new_space_.top();
+  Address from_limit = new_space_.limit();
+  if (from_top < from_limit) {
+    int remaining_in_page = static_cast<int>(from_limit - from_top);
+    CreateFillerObjectAt(from_top, remaining_in_page);
+  }
+}
+
+
 bool Heap::CollectGarbage(GarbageCollector collector,
                           const char* gc_reason,
                           const char* collector_reason,
@@ -789,17 +804,7 @@ bool Heap::CollectGarbage(GarbageCollector collector,
   allocation_timeout_ = Max(6, FLAG_gc_interval);
 #endif
 
-  // There may be an allocation memento behind every object in new space.
-  // If we evacuate a not full new space or if we are on the last page of
-  // the new space, then there may be uninitialized memory behind the top
-  // pointer of the new space page. We store a filler object there to
-  // identify the unused space.
-  Address from_top = new_space_.top();
-  Address from_limit = new_space_.limit();
-  if (from_top < from_limit) {
-    int remaining_in_page = static_cast<int>(from_limit - from_top);
-    CreateFillerObjectAt(from_top, remaining_in_page);
-  }
+  EnsureFillerObjectAtTop();
 
   if (collector == SCAVENGER && !incremental_marking()->IsStopped()) {
     if (FLAG_trace_incremental_marking) {
@@ -873,16 +878,6 @@ int Heap::NotifyContextDisposed() {
 }
 
 
-void Heap::PerformScavenge() {
-  GCTracer tracer(this, NULL, NULL);
-  if (incremental_marking()->IsStopped()) {
-    PerformGarbageCollection(SCAVENGER, &tracer);
-  } else {
-    PerformGarbageCollection(MARK_COMPACTOR, &tracer);
-  }
-}
-
-
 void Heap::MoveElements(FixedArray* array,
                         int dst_index,
                         int src_index,