Introduce nested deoptimization environments.

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
diff --git a/runtime/vm/flow_graph_optimizer.cc b/runtime/vm/flow_graph_optimizer.cc
index 27156e4ed15c60443fb5ec7ab7db902b488e2d84..700ef6e173e7d69b4c2fa59c16eefcefecd076ee 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -126,8 +126,8 @@ void FlowGraphOptimizer::SelectRepresentations() {
   GraphEntryInstr* graph_entry = block_order_[0]->AsGraphEntry();
 
   // Visit incoming parameters.
-  for (intptr_t i = 0; i < graph_entry->start_env()->values().length(); i++) {
-    Value* val = graph_entry->start_env()->values()[i];
+  for (intptr_t i = 0; i < graph_entry->start_env()->Length(); i++) {
+    Value* val = graph_entry->start_env()->ValueAt(i);
     InsertConversionsFor(val->definition());
   }
 
@@ -1085,8 +1085,8 @@ void FlowGraphTypePropagator::VisitGraphEntry(GraphEntryInstr* graph_entry) {
     return;
   }
   // Visit incoming parameters.
-  for (intptr_t i = 0; i < graph_entry->start_env()->values().length(); i++) {
-    Value* val = graph_entry->start_env()->values()[i];
+  for (intptr_t i = 0; i < graph_entry->start_env()->Length(); i++) {
+    Value* val = graph_entry->start_env()->ValueAt(i);
     ParameterInstr* param = val->definition()->AsParameter();
     if (param != NULL) {
       ASSERT(param->index() == i);