Modifies assertion for possibly null code pointer.

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
===================================================================
--- runtime/vm/pages.cc	(revision 29395)
+++ runtime/vm/pages.cc	(working copy)
@@ -384,7 +384,6 @@
 }
 
 
-
 class CodeDetacherVisitor : public ObjectVisitor {
  public:
   explicit CodeDetacherVisitor(Isolate* isolate) : ObjectVisitor(isolate) { }
@@ -392,20 +391,26 @@
   virtual void VisitObject(RawObject* obj);
 
  private:
+  static bool MayDetachCode(const Function& fn);
   DISALLOW_COPY_AND_ASSIGN(CodeDetacherVisitor);
 };
 
 
+bool CodeDetacherVisitor::MayDetachCode(const Function& fn) {
+  return fn.HasCode() &&  // Not already detached.
+         !fn.HasOptimizedCode() &&
+         !fn.HasBreakpoint() &&
+         (fn.usage_counter() > 0);
+}
+
+
 void CodeDetacherVisitor::VisitObject(RawObject* raw_obj) {
   Isolate* isolate = Isolate::Current();
   HANDLESCOPE(isolate);
   const Object& obj = Object::Handle(raw_obj);
   if (obj.GetClassId() == kFunctionCid) {
     const Function& fn = Function::Cast(obj);
-    if (!fn.HasOptimizedCode() &&
-        !fn.HasBreakpoint() &&
-        fn.HasCode() &&  // Not already detached.
-        (fn.usage_counter() > 0)) {
+    if (CodeDetacherVisitor::MayDetachCode(fn)) {
       fn.set_usage_counter(fn.usage_counter() / 2);
       if (fn.usage_counter() == 0) {
         if (FLAG_log_code_drop) {