add closed? method on Stream object to inspect the object's open/close state

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>

lib/sinatra/base.rb

@@ -332,6 +332,10 @@ module Sinatra
       end
 
       alias errback callback
+
+      def closed?
+        @closed
+      end
     end
 
     # Allows to start sending data to the client even though later parts of

test/streaming_test.rb

@@ -139,4 +139,11 @@ class StreamingTest < Test::Unit::TestCase
     get '/'
     assert ran
   end
+
+  it 'has a public interface to inspect its open/closed state' do
+    stream = Stream.new(Stream) { |out| out << :foo }
+    assert !stream.closed?
+    stream.close
+    assert stream.closed?
+  end
 end