Remove an unneeded hash_set from QuicAckNotifierManager.

net/quic/quic_ack_notifier_test.cc

Index: net/quic/quic_ack_notifier_test.cc
diff --git a/net/quic/quic_ack_notifier_test.cc b/net/quic/quic_ack_notifier_test.cc
index 5afbd6f5112e108c73ea50a095c34001bd735cbb..75d1b1e938f9be53624459ef37e92d214bd8e858 100644
--- a/net/quic/quic_ack_notifier_test.cc
+++ b/net/quic/quic_ack_notifier_test.cc
@@ -48,6 +48,15 @@ TEST_F(QuicAckNotifierTest, DoesNotTrigger) {
   EXPECT_FALSE(notifier_->OnAck(99, zero_));
 }
 
+// Should not trigger callback if we abandon all three packets.
+TEST_F(QuicAckNotifierTest, AbandonDoesNotTrigger) {
+  // Should not trigger callback as not all packets have been seen.
+  EXPECT_CALL(*delegate_, OnAckNotification(_, _, _)).Times(0);
+  EXPECT_FALSE(notifier_->OnPacketAbandoned());
+  EXPECT_FALSE(notifier_->OnPacketAbandoned());
+  EXPECT_TRUE(notifier_->OnPacketAbandoned());
+}
+
 // Should trigger even after updating sequence numbers and receiving ACKs for
 // new sequeunce numbers.
 TEST_F(QuicAckNotifierTest, UpdateSeqNums) {