Implement a variation of scalar replacement for non-escaping allocations.

runtime/vm/flow_graph_builder.cc

Index: runtime/vm/flow_graph_builder.cc
diff --git a/runtime/vm/flow_graph_builder.cc b/runtime/vm/flow_graph_builder.cc
index 85ed2104b637f6ce192679c9f7b0fe041f821c8e..1362a888e2c5776042bde25b61123e221cc05f38 100644
--- a/runtime/vm/flow_graph_builder.cc
+++ b/runtime/vm/flow_graph_builder.cc
@@ -292,6 +292,11 @@ void InlineExitCollector::ReplaceCall(TargetEntryInstr* callee_entry) {
       call_block->AddDominatedBlock(block);
     }
   }
+
+  // Neither call nor callee entry are in the graph at this point. Remove them
+  // from use lists.
+  callee_entry->UnuseAllInputs();
+  call_->UnuseAllInputs();
 }