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

runtime/vm/dart_api_state.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_DART_API_STATE_H_
 #define VM_DART_API_STATE_H_
 
 #include "include/dart_api.h"
 
 #include "platform/thread.h"
@@ skipping 197 matching lines @@
   Dart_WeakPersistentHandle apiHandle() {
     return reinterpret_cast<Dart_WeakPersistentHandle>(this);
   }
 
   void SetExternalSize(intptr_t size, Isolate* isolate) {
     ASSERT(size >= 0);
     set_external_size(Utils::RoundUp(size, kObjectAlignment));
     if (SpaceForExternal() == Heap::kNew) {
       SetExternalNewSpaceBit();
     }
-    // TODO(koda): On repeated/large external allocations for existing objects,
-    // without any intervening normal allocation, GC will not trigger.
     isolate->heap()->AllocateExternal(external_size(), SpaceForExternal());
   }
 
   // Called when the referent becomes unreachable.
   void UpdateUnreachable(Isolate* isolate) {
     EnsureFreeExternal(isolate);
     Finalize(isolate, this);
   }
 
   // Called when the referent has moved, potentially between generations.
   void UpdateRelocated(Isolate* isolate) {
     if (IsSetNewSpaceBit() && (SpaceForExternal() == Heap::kOld)) {
-      isolate->heap()->FreeExternal(external_size(), Heap::kNew);
-      isolate->heap()->AllocateExternal(external_size(), Heap::kOld);
+      isolate->heap()->PromoteExternal(external_size());
       ClearExternalNewSpaceBit();
     }
   }
 
   // Idempotent. Called when the handle is explicitly deleted or the
   // referent becomes unreachable.
   void EnsureFreeExternal(Isolate* isolate) {
     isolate->heap()->FreeExternal(external_size(), SpaceForExternal());
     set_external_size(0);
   }
@@ skipping 642 matching lines @@
           ApiNativeScope::Current()->zone()) {}
   ApiGrowableArray()
       : BaseGrowableArray<T, ValueObject>(
           ApiNativeScope::Current()->zone()) {}
 };
 
 
 }  // namespace dart
 
 #endif  // VM_DART_API_STATE_H_