VM: Always start switchable calls with IC stub.

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index cfdf133f10800f65a9b02ca5d425f155a2a0737b..d28c293506bf08c9c9cf46671e75395733284bef 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -1153,8 +1153,9 @@ void FlowGraphCompiler::GenerateInstanceCall(
     intptr_t argument_count,
     LocationSummary* locs,
     const ICData& ic_data_in) {
-  const ICData& ic_data = ICData::ZoneHandle(ic_data_in.Original());
+  ICData& ic_data = ICData::ZoneHandle(ic_data_in.Original());
   if (FLAG_precompiled_mode) {
+    ic_data = ic_data.AsUnaryClassChecks();
     EmitSwitchableInstanceCall(ic_data, argument_count,
                                deopt_id, token_pos, locs);
     return;