Fixes a couple problems with GC of unoptimized code.

runtime/vm/pages.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_PAGES_H_
 #define VM_PAGES_H_
 
 #include "vm/freelist.h"
 #include "vm/globals.h"
 #include "vm/virtual_memory.h"
@@ skipping 182 matching lines @@
   bool IsValidAddress(uword addr) const {
     return Contains(addr);
   }
 
   void VisitObjects(ObjectVisitor* visitor) const;
   void VisitObjectPointers(ObjectPointerVisitor* visitor) const;
 
   RawObject* FindObject(FindObjectVisitor* visitor,
                         HeapPage::PageType type) const;
 
-  // Runs a visitor that attempts to drop references to code that has not
-  // been run in awhile.
-  void TryDetachingCode();
+  // Checks if enough time has elapsed since the last attempt to collect
+  // code.
+  bool ShouldTryCollectingCode();
 
   // Collect the garbage in the page space using mark-sweep.
   void MarkSweep(bool invoke_api_callbacks);
 
   void StartEndAddress(uword* start, uword* end) const;
 
   void SetGrowthControlState(bool state) {
     page_space_controller_.set_is_enabled(state);
   }
 
@@ skipping 52 matching lines @@
   PageSpaceController page_space_controller_;
 
   friend class PageSpaceController;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageSpace);
 };
 
 }  // namespace dart
 
 #endif  // VM_PAGES_H_