In QuicFramer::ProcessIetfTimestampsInAckFrame, use the first timestamp_delta as is.

Split from cl/423075926.

PiperOrigin-RevId: 425374776

quic/core/quic_framer.cc

diff --git a/quic/core/quic_framer.cc b/quic/core/quic_framer.cc
index 6d2d9c7..45166ec 100644
--- a/quic/core/quic_framer.cc
+++ b/quic/core/quic_framer.cc
@@ -4161,7 +4161,7 @@
       // packet order.
       timestamp_delta = timestamp_delta << receive_timestamps_exponent_;
       if (i == 0 && j == 0) {
-        last_timestamp_ = CalculateTimestampFromWire(timestamp_delta);
+        last_timestamp_ = QuicTime::Delta::FromMicroseconds(timestamp_delta);
       } else {
         last_timestamp_ = last_timestamp_ -
                           QuicTime::Delta::FromMicroseconds(timestamp_delta);
@@ -4170,10 +4170,10 @@
           return false;
         }
       }
-      visitor_->OnAckTimestamp(packet_number - j,
-                               creation_time_ + last_timestamp_);
+      visitor_->OnAckTimestamp(packet_number, creation_time_ + last_timestamp_);
+      packet_number--;
     }
-    packet_number = packet_number - (timestamp_count - 1);
+    packet_number--;
   }
   return true;
 }

quic/core/quic_framer_test.cc

diff --git a/quic/core/quic_framer_test.cc b/quic/core/quic_framer_test.cc
index 207329c..cd3a487 100644
--- a/quic/core/quic_framer_test.cc
+++ b/quic/core/quic_framer_test.cc
@@ -4116,7 +4116,7 @@
 
        // Timestamp range 2 (one packet).
        { "Unable to read receive timestamp gap.",
-         { kVarInt62OneByte + 0x07 }},
+         { kVarInt62OneByte + 0x05 }},
        { "Unable to read receive timestamp count.",
          { kVarInt62OneByte + 0x01 }},
        { "Unable to read receive timestamp delta.",
@@ -4124,7 +4124,7 @@
 
        // Timestamp range 3 (two packets).
        { "Unable to read receive timestamp gap.",
-         { kVarInt62OneByte + 0x0a }},
+         { kVarInt62OneByte + 0x08 }},
        { "Unable to read receive timestamp count.",
          { kVarInt62OneByte + 0x02 }},
        { "Unable to read receive timestamp delta.",