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

src/mksnapshot.cc

Index: src/mksnapshot.cc
diff --git a/src/mksnapshot.cc b/src/mksnapshot.cc
index 82871c09b0740808266c25498490c841ba4f999c..d1620bfff57aa50ece036c3ab8411e2976e8e0a4 100644
--- a/src/mksnapshot.cc
+++ b/src/mksnapshot.cc
@@ -312,7 +312,7 @@ int main(int argc, char** argv) {
   }
   // If we don't do this then we end up with a stray root pointing at the
   // context even after we have disposed of the context.
-  HEAP->CollectAllGarbage(i::Heap::kNoGCFlags);
+  HEAP->CollectAllGarbage(i::Heap::kNoGCFlags, "mksnapshot");
   i::Object* raw_context = *(v8::Utils::OpenHandle(*context));
   context.Dispose();
   CppByteSink sink(argv[1]);