Handle conditional get in live requests - this will prevent error whe…

…n using stale on live streams(issue rails#9636)

actionpack/lib/action_controller/metal/live.rb

@@ -98,6 +98,10 @@ def build_buffer(response, body)
       def merge_default_headers(original, default)
         Header.new self, super
       end
+
+      def handle_conditional_get!
+        super unless committed?
+      end
     end
 
     def process(name)

actionpack/test/controller/live_stream_test.rb

@@ -48,6 +48,10 @@ def thread_locals
         end
         response.stream.close
       end
+
+      def with_stale
+        render :text => 'stale' if stale?(:etag => "123")
+      end
     end
 
     tests TestController
@@ -117,5 +121,16 @@ def test_render_text
       assert_equal 'zomg', response.body
       assert response.stream.closed?, 'stream should be closed'
     end
+
+    def test_stale_without_etag
+      get :with_stale
+      assert_equal 200, @response.status.to_i
+    end
+
+    def test_stale_with_etag
+      @request.if_none_match = Digest::MD5.hexdigest("123")
+      get :with_stale
+      assert_equal 304, @response.status.to_i
+    end
   end
 end