Optimize AOT's switchable calls for the monomorphic case.

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 05ddd32d1dbad48878a9551ee1e3f4d21abd717f..aecec1785327f1513bb4ccbf299957e19a5f43da 100644
--- a/runtime/vm/object_test.cc
+++ b/runtime/vm/object_test.cc
@@ -2713,7 +2713,7 @@ 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.EntryPoint();
+  uword entry_point = instructions.UncheckedEntryPoint();
   EXPECT_EQ(instructions.raw(), Instructions::FromEntryPoint(entry_point));
   const Object& result = Object::Handle(
       DartEntry::InvokeFunction(function, Array::empty_array()));
@@ -2731,7 +2731,7 @@ 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.EntryPoint();
+  uword entry_point = instructions.UncheckedEntryPoint();
   EXPECT_EQ(instructions.raw(), Instructions::FromEntryPoint(entry_point));
   // Try writing into the generated code, expected to crash.
   *(reinterpret_cast<char*>(entry_point) + 1) = 1;