Reland concurrent sweeping of code space.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 3340a0fd384a3cdf8bb9e11a90b00f9f00b3b249..04dd85588b65df88193ab0cd993640db72423844 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -509,6 +509,12 @@ const char* Heap::GetSpaceName(int idx) {
 
 
 void Heap::ClearAllICsByKind(Code::Kind kind) {
+  // If concurrent sweeping is in progress, we have to wait for the sweeper
+  // threads before we iterate the heap.
+  if (mark_compact_collector()->sweeping_in_progress()) {
+    mark_compact_collector()->EnsureSweepingCompleted();
+  }
+  // TODO(mvstanton): Do not iterate the heap.
   HeapObjectIterator it(code_space());
 
   for (Object* object = it.Next(); object != NULL; object = it.Next()) {
@@ -5157,6 +5163,11 @@ void Heap::Verify() {
   code_space_->Verify(&no_dirty_regions_visitor);
 
   lo_space_->Verify();
+
+  mark_compact_collector_.VerifyWeakEmbeddedObjectsInCode();
+  if (FLAG_omit_map_checks_for_leaf_maps) {
+    mark_compact_collector_.VerifyOmittedMapChecks();
+  }
 }
 #endif