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

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/spaces.h"
@@ skipping 181 matching lines @@
   };
 
   PageSpace(Heap* heap, intptr_t max_capacity_in_words);
   ~PageSpace();
 
   uword TryAllocate(intptr_t size,
                     HeapPage::PageType type = HeapPage::kData,
                     GrowthPolicy growth_policy = kControlGrowth);
 
   bool NeedsGarbageCollection() const {
-    return page_space_controller_.NeedsGarbageCollection(usage_);
+    return page_space_controller_.NeedsGarbageCollection(usage_) ||
+           NeedsExternalGC();
   }
 
   intptr_t UsedInWords() const { return usage_.used_in_words; }
   intptr_t CapacityInWords() const { return usage_.capacity_in_words; }
   intptr_t ExternalInWords() const {
     return usage_.external_in_words;
   }
   SpaceUsage GetCurrentUsage() const { return usage_; }
 
   bool Contains(uword addr) const;
@@ skipping 22 matching lines @@
       page_space_controller_.Enable(usage_);
     } else {
       page_space_controller_.Disable();
     }
   }
 
   bool GrowthControlState() {
     return page_space_controller_.is_enabled();
   }
 
-  bool NeedExternalGC() {
+  bool NeedsExternalGC() const {
     return UsedInWords() + ExternalInWords() > max_capacity_in_words_;
   }
 
   void WriteProtect(bool read_only);
 
   void AddGCTime(int64_t micros) {
     gc_time_micros_ += micros;
   }
 
   int64_t gc_time_micros() const {
@@ skipping 65 matching lines @@
   intptr_t collections_;
 
   friend class PageSpaceController;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageSpace);
 };
 
 }  // namespace dart
 
 #endif  // VM_PAGES_H_