Simplify code in code code generator, move checks to flow graph builder. We can assume that any typ…

runtime/vm/flow_graph_builder.h

Index: runtime/vm/flow_graph_builder.h
===================================================================
--- runtime/vm/flow_graph_builder.h	(revision 6529)
+++ runtime/vm/flow_graph_builder.h	(working copy)
@@ -156,7 +156,7 @@
   Value* BuildInstantiatorTypeArguments(intptr_t token_index,
                                         intptr_t start_index);
 
-  void BuildInstanceOf(ComparisonNode* node);
+  virtual void BuildInstanceOf(ComparisonNode* node);
 
   bool MustSaveRestoreContext(SequenceNode* node) const;
 
@@ -240,6 +240,8 @@
 
   virtual void CompiletimeStringInterpolation(const Function& interpol_func,
                                               const Array& literals);
+
+  virtual void BuildInstanceOf(ComparisonNode* node);
 };