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

src/extensions/gc-extension.cc

Index: src/extensions/gc-extension.cc
diff --git a/src/extensions/gc-extension.cc b/src/extensions/gc-extension.cc
index 54c8cdc0c80bf0ac57fb78c19868f7c90c7fa45b..573797e174aae23ba2ee800e972fd8fa5835c4a0 100644
--- a/src/extensions/gc-extension.cc
+++ b/src/extensions/gc-extension.cc
@@ -40,7 +40,7 @@ v8::Handle<v8::FunctionTemplate> GCExtension::GetNativeFunction(
 
 
 v8::Handle<v8::Value> GCExtension::GC(const v8::Arguments& args) {
-  HEAP->CollectAllGarbage(Heap::kNoGCFlags);
+  HEAP->CollectAllGarbage(Heap::kNoGCFlags, "gc extension");
   return v8::Undefined();
 }