Propagate this-specialization to regular (megamorphic) calls

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index 54501a4f1d3d17e024e4e8a149fd4bc076ec8cdd..5f837bf9219f634e99772f38893d076ac8fe362e 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -2742,6 +2742,8 @@ class InstanceCallInstr : public TemplateDefinition<0, Throws> {
 
   virtual bool CanDeoptimize() const { return true; }
 
+  virtual Definition* Canonicalize(FlowGraph* flow_graph);
+
   virtual bool CanBecomeDeoptimizationTarget() const {
     // Instance calls that are specialized by the optimizer need a
     // deoptimization descriptor before the call.