Reland of land 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 80b28d195bf73d6055ac1ef3c6fa74200de866ec..6fa87704bbf0e7cedf37f6da08a4bdc4d9196c40 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -509,6 +509,7 @@
 
 
 void Heap::ClearAllICsByKind(Code::Kind kind) {
+  // TODO(mvstanton): Do not iterate the heap.
   HeapObjectIterator it(code_space());
 
   for (Object* object = it.Next(); object != NULL; object = it.Next()) {
@@ -5250,6 +5251,11 @@
   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