Use ConnectionErrorObserver, not callbacks, for error handling.

blimp/net/blimp_message_output_buffer_unittest.cc

Index: blimp/net/blimp_message_output_buffer_unittest.cc
diff --git a/blimp/net/blimp_message_output_buffer_unittest.cc b/blimp/net/blimp_message_output_buffer_unittest.cc
index 6db7ec2a2aec04abae594ee953f7e763cf1eac73..064ed900397d60d687ae3f2732c13f57a345f867 100644
--- a/blimp/net/blimp_message_output_buffer_unittest.cc
+++ b/blimp/net/blimp_message_output_buffer_unittest.cc
@@ -185,11 +185,11 @@ TEST_F(BlimpMessageOutputBufferTest, WriteError) {
                           complete_cb_1.callback());
   ASSERT_EQ(1, buffer_->GetBufferByteSizeForTest());
 
-  // First write attempt, which fails.
+  // First write attempt, which fails. The output buffer isn't notified of the
+  // connection loss, because the write callback is silently dropped.
   ASSERT_TRUE(captured_cb_.is_null());
   buffer_->SetOutputProcessor(&output_processor_);
   ASSERT_FALSE(captured_cb_.is_null());
-  base::ResetAndReturn(&captured_cb_).Run(net::ERR_FAILED);
   ASSERT_EQ(1, buffer_->GetBufferByteSizeForTest());
   ASSERT_EQ(0, buffer_->GetUnacknowledgedMessageCountForTest());