Disable hoisting CheckClass due to excessive deoptimization.

runtime/vm/object.h

Index: runtime/vm/object.h
===================================================================
--- runtime/vm/object.h	(revision 32457)
+++ runtime/vm/object.h	(working copy)
@@ -1722,6 +1722,11 @@
   }
   void set_is_redirecting(bool value) const;
 
+  bool allows_hoisting_check_class() const {
+    return AllowsHoistingCheckClassBit::decode(raw_ptr()->kind_tag_);
+  }
+  void set_allows_hoisting_check_class(bool value) const;
+
   bool HasOptimizedCode() const;
 
   // Returns true if the argument counts are valid for calling this function.
@@ -1892,6 +1897,7 @@
     kNativeBit = 12,
     kRedirectingBit = 13,
     kExternalBit = 14,
+    kAllowsHoistingCheckClassBit = 15,
   };
   class KindBits :
     public BitField<RawFunction::Kind, kKindTagBit, kKindTagSize> {};  // NOLINT
@@ -1906,6 +1912,8 @@
   class NativeBit : public BitField<bool, kNativeBit, 1> {};
   class ExternalBit : public BitField<bool, kExternalBit, 1> {};
   class RedirectingBit : public BitField<bool, kRedirectingBit, 1> {};
+  class AllowsHoistingCheckClassBit :
+      public BitField<bool, kAllowsHoistingCheckClassBit, 1> {};  // NOLINT
 
   void set_name(const String& value) const;
   void set_kind(RawFunction::Kind value) const;