Support FrameLookup vm test on ARM, requiring among other things:

runtime/vm/stub_code_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"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
@@ skipping 1069 matching lines @@
       // Set RBX to new object end.
       __ movq(RBX, RCX);
       __ Bind(&type_arguments_ready);
       // RAX: new object.
       // RDI: new object type arguments.
     }
 
     // RAX: new object start.
     // RBX: next object start.
     // RDI: new object type arguments (if is_cls_parameterized).
-    __ LoadObject(RDX, cls);  // Load class of object to be allocated.
     // Set the tags.
     uword tags = 0;
     tags = RawObject::SizeTag::update(instance_size, tags);
     ASSERT(cls.id() != kIllegalCid);
     tags = RawObject::ClassIdTag::update(cls.id(), tags);
     __ movq(Address(RAX, Instance::tags_offset()), Immediate(tags));
 
     // Initialize the remaining words of the object.
     const Immediate& raw_null =
         Immediate(reinterpret_cast<intptr_t>(Object::null()));
 
     // RAX: new object start.
     // RBX: next object start.
-    // RDX: class of the object to be allocated.
     // RDI: new object type arguments (if is_cls_parameterized).
     // First try inlining the initialization without a loop.
     if (instance_size < (kInlineInstanceSize * kWordSize)) {
       // Check if the object contains any non-header fields.
       // Small objects are initialized using a consecutive set of writes.
       for (intptr_t current_offset = sizeof(RawObject);
            current_offset < instance_size;
            current_offset += kWordSize) {
         __ movq(Address(RAX, current_offset), raw_null);
       }
@@ skipping 959 matching lines @@
   __ cmpq(left, right);
   __ Bind(&done);
   __ popq(right);
   __ popq(left);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64