Restore 0-based temporary index numbering in the VM compiler.

runtime/vm/flow_graph_builder.h

Index: runtime/vm/flow_graph_builder.h
diff --git a/runtime/vm/flow_graph_builder.h b/runtime/vm/flow_graph_builder.h
index c69e4390e0ef9ffff34d879f80c6cb53b0d59bca..bcadb62daffe7d5a6cf212a93d9271d255c6513b 100644
--- a/runtime/vm/flow_graph_builder.h
+++ b/runtime/vm/flow_graph_builder.h
@@ -161,7 +161,7 @@ class FlowGraphBuilder: public ValueObject {
   }
 
   intptr_t temp_count() const { return temp_count_; }
-  intptr_t AllocateTemp() { return ++temp_count_; }
+  intptr_t AllocateTemp() { return temp_count_++; }
   void DeallocateTemps(intptr_t count) {
     ASSERT(temp_count_ >= count);
     temp_count_ -= count;