Don't require eliminating certain type checks in unoptimized compilation.

runtime/vm/flow_graph_compiler_x64.cc

Index: runtime/vm/flow_graph_compiler_x64.cc
===================================================================
--- runtime/vm/flow_graph_compiler_x64.cc	(revision 36662)
+++ runtime/vm/flow_graph_compiler_x64.cc	(working copy)
@@ -25,7 +25,6 @@
 DECLARE_FLAG(int, optimization_counter_threshold);
 DECLARE_FLAG(int, reoptimization_counter_threshold);
 DECLARE_FLAG(bool, enable_type_checks);
-DECLARE_FLAG(bool, eliminate_type_checks);
 DECLARE_FLAG(bool, enable_simd_inline);
 
 
@@ -661,13 +660,6 @@
   __ CompareObject(RAX, Object::null_object(), PP);
   __ j(EQUAL, &is_assignable);
 
-  if (!FLAG_eliminate_type_checks || dst_type.IsMalformed()) {
-    // If type checks are not eliminated during the graph building then
-    // a transition sentinel can be seen here.
-    __ CompareObject(RAX, Object::transition_sentinel(), PP);
-    __ j(EQUAL, &is_assignable);
-  }
-
   // Generate throw new TypeError() if the type is malformed or malbounded.
   if (dst_type.IsMalformedOrMalbounded()) {
     __ PushObject(Object::ZoneHandle(), PP);  // Make room for the result.