Tweak compaction candidate selection to avoid keeping page with low occupancy around.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 4059 matching lines @@
   // continue to call IdleNotification.
   i::Isolate* isolate = i::Isolate::Current();
   if (isolate == NULL || !isolate->IsInitialized()) return true;
   return i::V8::IdleNotification(hint);
 }
 
 
 void v8::V8::LowMemoryNotification() {
   i::Isolate* isolate = i::Isolate::Current();
   if (isolate == NULL || !isolate->IsInitialized()) return;
-  isolate->heap()->CollectAllAvailableGarbage();
+  isolate->heap()->CollectAllAvailableGarbage("low memory notification");
 }
 
 
 int v8::V8::ContextDisposedNotification() {
   i::Isolate* isolate = i::Isolate::Current();
   if (!isolate->IsInitialized()) return 0;
   return isolate->heap()->NotifyContextDisposed();
 }
 
 
@@ skipping 2097 matching lines @@
 
 
 char* HandleScopeImplementer::Iterate(ObjectVisitor* v, char* storage) {
   HandleScopeImplementer* scope_implementer =
       reinterpret_cast<HandleScopeImplementer*>(storage);
   scope_implementer->IterateThis(v);
   return storage + ArchiveSpacePerThread();
 }
 
 } }  // namespace v8::internal