Revert revision 27542 "Make Dart_IdentityEqual live up to its spec and not leak boxing implementati…

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 27544)
+++ runtime/vm/object.cc	(working copy)
@@ -10358,24 +10358,6 @@
 }
 
 
-bool Instance::IsIdenticalTo(const Instance& other) const {
-  if (raw() == other.raw()) return true;
-  if (IsInteger() && other.IsInteger()) {
-    return Equals(other);
-  }
-  if (IsDouble() && other.IsDouble()) {
-    if (Equals(other)) return true;
-    // Check for NaN.
-    const Double& a_double = Double::Cast(*this);
-    const Double& b_double = Double::Cast(other);
-    if (isnan(a_double.value()) && isnan(b_double.value())) {
-      return true;
-    }
-  }
-  return false;
-}
-
-
 void Instance::SetNativeField(int index, intptr_t value) const {
   ASSERT(IsValidNativeIndex(index));
   Object& native_fields = Object::Handle(*NativeFieldsAddr());