Remove default monomorphic check code from functions and stubs that do not need it.

runtime/vm/object_test.cc

Index: runtime/vm/object_test.cc
diff --git a/runtime/vm/object_test.cc b/runtime/vm/object_test.cc
index 86852f41562ec11f98262d59e7196e93f5ce9c8d..0cd21eaf6006a7a421018be5cecdc3b2bfd232c9 100644
--- a/runtime/vm/object_test.cc
+++ b/runtime/vm/object_test.cc
@@ -2721,9 +2721,8 @@ VM_TEST_CASE(Code) {
   Code& code = Code::Handle(Code::FinalizeCode(function, &_assembler_));
   function.AttachCode(code);
   const Instructions& instructions = Instructions::Handle(code.instructions());
-  uword entry_point = instructions.UncheckedEntryPoint();
-  EXPECT_EQ(instructions.raw(),
-            Instructions::FromUncheckedEntryPoint(entry_point));
+  uword payload_start = instructions.PayloadStart();
+  EXPECT_EQ(instructions.raw(), Instructions::FromPayloadStart(payload_start));
   const Object& result = Object::Handle(
       DartEntry::InvokeFunction(function, Array::empty_array()));
   EXPECT_EQ(1, Smi::Cast(result).Value());
@@ -2740,11 +2739,10 @@ VM_TEST_CASE(CodeImmutability) {
   Code& code = Code::Handle(Code::FinalizeCode(function, &_assembler_));
   function.AttachCode(code);
   Instructions& instructions = Instructions::Handle(code.instructions());
-  uword entry_point = instructions.UncheckedEntryPoint();
-  EXPECT_EQ(instructions.raw(),
-            Instructions::FromUncheckedEntryPoint(entry_point));
+  uword payload_start = instructions.PayloadStart();
+  EXPECT_EQ(instructions.raw(), Instructions::FromPayloadStart(payload_start));
   // Try writing into the generated code, expected to crash.
-  *(reinterpret_cast<char*>(entry_point) + 1) = 1;
+  *(reinterpret_cast<char*>(payload_start) + 1) = 1;
   if (!FLAG_write_protect_code) {
     // Since this test is expected to crash, crash if write protection of code
     // is switched off.