Ensure that safepoints are assigned to the live ranges of constants.

runtime/vm/flow_graph_allocator.cc

Index: runtime/vm/flow_graph_allocator.cc
diff --git a/runtime/vm/flow_graph_allocator.cc b/runtime/vm/flow_graph_allocator.cc
index a347c8f1e30f438ac4cad9e1a1f5de30afd367dc..5125f971ce1b8ad6f57ce4dd3ad3ed4afd7f0ab7 100644
--- a/runtime/vm/flow_graph_allocator.cc
+++ b/runtime/vm/flow_graph_allocator.cc
@@ -522,13 +522,13 @@ void FlowGraphAllocator::BuildLiveRanges() {
         spill_slots_.Add(range->End());
         quad_spill_slots_.Add(false);
       }
-      AssignSafepoints(range);
     } else {
       ConstantInstr* constant = defn->AsConstant();
       ASSERT(constant != NULL);
       range->set_assigned_location(Location::Constant(constant->value()));
       range->set_spill_slot(Location::Constant(constant->value()));
     }
+    AssignSafepoints(range);
     range->finger()->Initialize(range);
     UsePosition* use =
         range->finger()->FirstRegisterBeneficialUse(graph_entry->start_pos());