Implement basic support for deferred slow path code with calls that save and restore live registers.

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 452c56531fdc4d2f61cef04feed6f9164bdae605..b24028dc0a904457a6096e86baf3dc4adb390599 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -716,7 +716,7 @@ void FlowGraphAnalyzer::Analyze() {
     BlockEntryInstr* entry = blocks_[i];
     for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
       LocationSummary* locs = it.Current()->locs();
-      if ((locs != NULL) && locs->is_call()) {
+      if ((locs != NULL) && locs->contains_call()) {
         is_leaf_ = false;
         return;
       }