Use PassiveObject were possible.

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 39611)
+++ runtime/vm/object.cc	(working copy)
@@ -13096,14 +13096,14 @@
   const Function& eval_func =
       Function::Handle(EvaluateHelper(cls, expr, param_names, false));
   const Array& args = Array::Handle(Array::New(1 + param_values.Length()));
-  Object& param = Object::Handle();
+  PassiveObject& param = PassiveObject::Handle();
   args.SetAt(0, *this);
   for (intptr_t i = 0; i < param_values.Length(); i++) {
     param = param_values.At(i);
     args.SetAt(i + 1, param);
   }
-  const Object& result =
-      Object::Handle(DartEntry::InvokeFunction(eval_func, args));
+  const PassiveObject& result =
+      PassiveObject::Handle(DartEntry::InvokeFunction(eval_func, args));
   return result.raw();
 }
 
@@ -13335,8 +13335,8 @@
 bool Instance::OperatorEquals(const Instance& other) const {
   // TODO(koda): Optimize for all builtin classes and all classes
   // that do not override operator==.
-  const Object& result =
-      Object::Handle(DartLibraryCalls::Equals(*this, other));
+  const PassiveObject& result =
+      PassiveObject::Handle(DartLibraryCalls::Equals(*this, other));
   return result.raw() == Object::bool_true().raw();

[Ivan Posva, 2014/08/28 19:31:53]

I don't think we need to wrap it in a handle to compare the raw values with a VM
predefined object.

[siva, 2014/08/29 00:17:01]

Done.

 }
 
@@ -18124,7 +18124,7 @@
   }
   ASSERT(new_length >= len);  // Cannot copy 'source' into new array.
   ASSERT(new_length != len);  // Unnecessary copying of array.
-  Object& obj = Object::Handle();
+  PassiveObject& obj = PassiveObject::Handle();
   for (int i = 0; i < len; i++) {
     obj = source.At(i);
     result.SetAt(i, obj);
@@ -18244,7 +18244,7 @@
   ASSERT(Length() > 0);
   intptr_t index = Length() - 1;
   const Array& contents = Array::Handle(data());
-  const Object& obj = Object::Handle(contents.At(index));
+  const PassiveObject& obj = PassiveObject::Handle(contents.At(index));
   contents.SetAt(index, Object::null_object());
   SetLength(index);
   return obj.raw();
@@ -18406,7 +18406,7 @@
 RawObject* LinkedHashMap::LookUp(const Object& key) const {
   ASSERT(!IsNull());
   EnumIndexDefaultMap map(data());
-  const Object& result = Object::Handle(map.GetOrNull(key));
+  const PassiveObject& result = PassiveObject::Handle(map.GetOrNull(key));
   ASSERT(map.Release().raw() == data());

[Ivan Posva, 2014/08/28 19:31:53]

You could stick the ASSERT in a NoGCScope and then we do not need to
wrap/unwrap.

[siva, 2014/08/29 00:17:01]

Done.

   return result.raw();
 }
@@ -18425,7 +18425,7 @@
   ASSERT(!IsNull());
   EnumIndexDefaultMap map(data());
   // TODO(koda): Make 'Remove' also return the old value.
-  const Object& result = Object::Handle(map.GetOrNull(key));
+  const PassiveObject& result = PassiveObject::Handle(map.GetOrNull(key));
   if (map.Remove(key)) {
     SetModified();
   }
@@ -19109,7 +19109,7 @@
   set_pc_offset_array(pc_offset_array);
   // Now append the new function and code list to the existing arrays.
   intptr_t j = start_index;
-  Object& obj = Object::Handle();
+  PassiveObject& obj = PassiveObject::Handle();
   for (intptr_t i = old_length; i < new_length; i++, j++) {
     obj = code_list.At(j);
     code_array.SetAt(i, obj);