FIX: severe memory leak in WeakValueMap

entries were not being cleaned up correctly from the backing store

lib/v8/weak.rb

@@ -39,7 +39,18 @@ def [](key)
  end
 
  def []=(key, value)
- @values[key] = V8::Weak::Ref.new(value)
+ ref = V8::Weak::Ref.new(value)
+ ObjectSpace.define_finalizer(value, self.class.ensure_cleanup(@values, key, ref))
+
+ @values[key] = ref
+ end
+
+ private
+
+ def self.ensure_cleanup(values,key,ref)
+ proc {
+ values.delete(key) if values[key] == ref
+ }
  end
  end
  end