Remove unused return value from QuicAlarm::Delegate::OnAlarm. No behavior change, not protected.

net/quic/quic_chromium_connection_helper_test.cc

Index: net/quic/quic_chromium_connection_helper_test.cc
diff --git a/net/quic/quic_chromium_connection_helper_test.cc b/net/quic/quic_chromium_connection_helper_test.cc
index aefa22ac90e3299f1dbb55f1e965cb38db859a7f..9fab8fb50d1d4be43c9762301413fde14d6c5d95 100644
--- a/net/quic/quic_chromium_connection_helper_test.cc
+++ b/net/quic/quic_chromium_connection_helper_test.cc
@@ -17,10 +17,7 @@ class TestDelegate : public QuicAlarm::Delegate {
  public:
   TestDelegate() : fired_(false) {}
 
-  QuicTime OnAlarm() override {
-    fired_ = true;
-    return QuicTime::Zero();
-  }
+  void OnAlarm() override { fired_ = true; }
 
   bool fired() const { return fired_; }
   void Clear() { fired_ = false; }