Use symbols when looking up fields in a class

runtime/vm/intrinsifier_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 1475 matching lines @@
 //    var state = ((_A * (_state[kSTATE_LO])) + _state[kSTATE_HI]) & _MASK_64;
 //    _state[kSTATE_LO] = state & _MASK_32;
 //    _state[kSTATE_HI] = state >> 32;
 void Intrinsifier::Random_nextState(Assembler* assembler) {
   const Library& math_lib = Library::Handle(Library::MathLibrary());
   ASSERT(!math_lib.IsNull());
   const Class& random_class = Class::Handle(
       math_lib.LookupClassAllowPrivate(Symbols::_Random()));
   ASSERT(!random_class.IsNull());
   const Field& state_field = Field::ZoneHandle(
-      random_class.LookupInstanceField(Symbols::_state()));
+      random_class.LookupInstanceFieldAllowPrivate(Symbols::_state()));
   ASSERT(!state_field.IsNull());
   const Field& random_A_field = Field::ZoneHandle(
-      random_class.LookupStaticField(Symbols::_A()));
+      random_class.LookupStaticFieldAllowPrivate(Symbols::_A()));
   ASSERT(!random_A_field.IsNull());
   ASSERT(random_A_field.is_const());
   const Instance& a_value = Instance::Handle(random_A_field.StaticValue());
   const int64_t a_int_value = Integer::Cast(a_value).AsInt64Value();
   // Receiver.
   __ movq(RAX, Address(RSP, + 1 * kWordSize));
   // Field '_state'.
   __ movq(RBX, FieldAddress(RAX, state_field.Offset()));
   // Addresses of _state[0] and _state[1].
   const intptr_t scale = Instance::ElementSizeFor(kTypedDataUint32ArrayCid);
@@ skipping 607 matching lines @@
   __ LoadIsolate(RAX);
   __ movq(RAX, Address(RAX, Isolate::current_tag_offset()));
   __ ret();
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64