Simpler, more consistent triggering of old GC; also, use external in policy.

runtime/vm/scavenger.h

 // Copyright (c) 2012, 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_SCAVENGER_H_
 #define VM_SCAVENGER_H_
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/flags.h"
@@ skipping 80 matching lines @@
   }
 
   void VisitObjects(ObjectVisitor* visitor) const;
   void VisitObjectPointers(ObjectPointerVisitor* visitor) const;
 
   void StartEndAddress(uword* start, uword* end) const {
     *start = to_->start();
     *end = to_->end();
   }
 
-  // Returns true if the last scavenge had a promotion failure.
-  bool HadPromotionFailure() {
-    return had_promotion_failure_;
-  }
-
   void WriteProtect(bool read_only);
 
   void AddGCTime(int64_t micros) {
     gc_time_micros_ += micros;
   }
 
   int64_t gc_time_micros() const {
     return gc_time_micros_;
   }
 
@@ skipping 86 matching lines @@
   uword resolved_top_;
 
   // Objects below this address have survived a scavenge.
   uword survivor_end_;
 
   // All object are aligned to this value.
   uword object_alignment_;
 
   // Keep track whether a scavenge is currently running.
   bool scavenging_;
-  // Keep track whether the scavenge had a promotion failure.
-  bool had_promotion_failure_;
 
   int64_t gc_time_micros_;
   intptr_t collections_;
 
   // The total size of external data associated with objects in this scavenger.
   intptr_t external_size_;
 
   friend class ScavengerVisitor;
   friend class ScavengerWeakVisitor;
 
   DISALLOW_COPY_AND_ASSIGN(Scavenger);
 };
 
 }  // namespace dart
 
 #endif  // VM_SCAVENGER_H_