Integrate concurrent sweeping with incremental marking.

BUG=

Review URL: https://codereview.chromium.org/12527011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13852 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/heap.h

@@ -1695,6 +1695,12 @@ class Heap {
     return sweeping_complete;
   }
 
+  bool EnsureSweepersProgressed(int step_size) {
+    bool sweeping_complete = old_data_space()->EnsureSweeperProgress(step_size);
+    sweeping_complete &= old_pointer_space()->EnsureSweeperProgress(step_size);
+    return sweeping_complete;
+  }
+
   ExternalStringTable* external_string_table() {
     return &external_string_table_;
   }

src/incremental-marking.cc

@@ -562,7 +562,6 @@ void IncrementalMarking::UncommitMarkingDeque() {
 
 
 void IncrementalMarking::Start() {
-  ASSERT(!heap_->mark_compact_collector()->IsConcurrentSweepingInProgress());
   if (FLAG_trace_incremental_marking) {
     PrintF("[IncrementalMarking] Start\n");
   }
@@ -901,7 +900,7 @@ void IncrementalMarking::Step(intptr_t allocated_bytes,
   }
 
   if (state_ == SWEEPING) {
-    if (heap_->AdvanceSweepers(static_cast<int>(bytes_to_process))) {
+    if (heap_->EnsureSweepersProgressed(static_cast<int>(bytes_to_process))) {
       bytes_scanned_ = 0;
       StartMarking(PREVENT_COMPACTION);
     }