Reduce QUIC load balancer copies by passing the result as an argument.

Code is not in production.

Performance numbers (Unenc/3 pass/1 pass, ns)
Tip of tree: 20.2 / 103 / 33.2
This CL: 21.4 / 101/ 26.3

PiperOrigin-RevId: 599890068
diff --git a/quiche/quic/load_balancer/load_balancer_server_id_test.cc b/quiche/quic/load_balancer/load_balancer_server_id_test.cc
index 08b5e6d..6b3bc52 100644
--- a/quiche/quic/load_balancer/load_balancer_server_id_test.cc
+++ b/quiche/quic/load_balancer/load_balancer_server_id_test.cc
@@ -30,27 +30,11 @@
                                    absl::Span<const uint8_t>(kRawServerId, 16))
                                    .IsValid()),
                   "Attempted to create LoadBalancerServerId with length 16");
-  EXPECT_QUIC_BUG(EXPECT_FALSE(LoadBalancerServerId(
-                                   absl::Span<const uint8_t>(kRawServerId, 9),
-                                   absl::Span<const uint8_t>(kRawServerId, 7))
-                                   .IsValid()),
-                  "Attempted to create LoadBalancerServerId with length 16");
   EXPECT_QUIC_BUG(
       EXPECT_FALSE(LoadBalancerServerId(absl::Span<const uint8_t>()).IsValid()),
       "Attempted to create LoadBalancerServerId with length 0");
 }
 
-TEST_F(LoadBalancerServerIdTest, TwoPartConstructor) {
-  LoadBalancerServerId server_id1(absl::Span<const uint8_t>(kRawServerId, 15));
-  ASSERT_TRUE(server_id1.IsValid());
-  LoadBalancerServerId server_id2(
-      absl::Span<const uint8_t>(kRawServerId, 8),
-      absl::Span<const uint8_t>(&kRawServerId[8], 7));
-  ASSERT_TRUE(server_id2.IsValid());
-  EXPECT_TRUE(server_id1 == server_id2);
-  ;
-}
-
 TEST_F(LoadBalancerServerIdTest, CompareIdenticalExceptLength) {
   LoadBalancerServerId server_id(absl::Span<const uint8_t>(kRawServerId, 15));
   ASSERT_TRUE(server_id.IsValid());
@@ -111,6 +95,18 @@
   }));
 }
 
+TEST_F(LoadBalancerServerIdTest, SetLengthInvalid) {
+  LoadBalancerServerId server_id;
+  EXPECT_QUIC_BUG(server_id.set_length(16),
+                  "Attempted to set LoadBalancerServerId length to 16");
+  EXPECT_QUIC_BUG(server_id.set_length(0),
+                  "Attempted to set LoadBalancerServerId length to 0");
+  server_id.set_length(1);
+  EXPECT_EQ(server_id.length(), 1);
+  server_id.set_length(15);
+  EXPECT_EQ(server_id.length(), 15);
+}
+
 }  // namespace
 
 }  // namespace test