Fixes a couple problems with GC of unoptimized code.

runtime/vm/raw_object.cc

Index: runtime/vm/raw_object.cc
===================================================================
--- runtime/vm/raw_object.cc	(revision 30197)
+++ runtime/vm/raw_object.cc	(working copy)
@@ -366,9 +366,36 @@
 }
 
 
+bool RawFunction::MayTrySkippingCode(RawFunction* raw_fun) {
+  Function fn;
+  fn = raw_fun;
+
+  Code code;
+  code = fn.CurrentCode();
+
+  // TODO(zra): If we would return true here, instead halve the usage counter,
+  //            and return true only if the counter is then zero. Otherwise
+  //            return false. For now, while testing, always skip the function's
+  //            code pointer when usage_counter > 0.
+
+  return fn.HasCode() &&  // Not already detached.
+         !code.is_optimized() &&
+         !fn.HasBreakpoint() &&
+         (fn.usage_counter() > 0);
+}
+
+
 intptr_t RawFunction::VisitFunctionPointers(RawFunction* raw_obj,
                                             ObjectPointerVisitor* visitor) {
-  visitor->VisitPointers(raw_obj->from(), raw_obj->to());
+  if (visitor->visit_function_code() ||
+      !RawFunction::MayTrySkippingCode(raw_obj)) {
+    visitor->VisitPointers(raw_obj->from(), raw_obj->to());
+  } else {
+    GrowableArray<RawFunction*>* sfga = visitor->skipped_code_functions();
+    ASSERT(sfga != NULL);
+    sfga->Add(raw_obj);
+    visitor->VisitPointers(raw_obj->from(), raw_obj->to_no_code());
+  }
   return Function::InstanceSize();
 }