Use overloaded operators with QuicTime for addition, subtraction and scalar

net/quic/quic_headers_stream.cc

Index: net/quic/quic_headers_stream.cc
diff --git a/net/quic/quic_headers_stream.cc b/net/quic/quic_headers_stream.cc
index 72c3ac9bbefd189fae366cf501f64a5943cb0b53..7cee686211a0a48a44dd87405a436824fac252d0 100644
--- a/net/quic/quic_headers_stream.cc
+++ b/net/quic/quic_headers_stream.cc
@@ -35,14 +35,14 @@ class HeaderTableDebugVisitor : public HpackHeaderTable::DebugVisitorInterface {
 
   int64_t OnNewEntry(const HpackEntry& entry) override {
     DVLOG(1) << entry.GetDebugString();
-    return clock_->ApproximateNow().Subtract(QuicTime::Zero()).ToMicroseconds();
+    return (clock_->ApproximateNow() - QuicTime::Zero()).ToMicroseconds();
   }
 
   void OnUseEntry(const HpackEntry& entry) override {
     const QuicTime::Delta elapsed(
-        clock_->ApproximateNow()
-            .Subtract(QuicTime::Delta::FromMicroseconds(entry.time_added()))
-            .Subtract(QuicTime::Zero()));
+        clock_->ApproximateNow() -
+        QuicTime::Delta::FromMicroseconds(entry.time_added()) -
+        QuicTime::Zero());
     DVLOG(1) << entry.GetDebugString() << " " << elapsed.ToMilliseconds()
              << " ms";
     headers_stream_hpack_visitor_->OnUseEntry(elapsed);
@@ -405,7 +405,7 @@ void QuicHeadersStream::OnControlFrameHeaderData(SpdyStreamId stream_id,
         // headers from lower numbered streams actually came off the
         // wire after headers for the current stream, hence there was
         // HOL blocking.
-        QuicTime::Delta delta(prev_max_timestamp_.Subtract(cur_max_timestamp_));
+        QuicTime::Delta delta = prev_max_timestamp_ - cur_max_timestamp_;
         DVLOG(1) << "stream " << stream_id
                  << ": Net.QuicSession.HeadersHOLBlockedTime "
                  << delta.ToMilliseconds();
@@ -452,7 +452,7 @@ void QuicHeadersStream::OnHeaderList(const QuicHeaderList& header_list) {
       // headers from lower numbered streams actually came off the
       // wire after headers for the current stream, hence there was
       // HOL blocking.
-      QuicTime::Delta delta = prev_max_timestamp_.Subtract(cur_max_timestamp_);
+      QuicTime::Delta delta = prev_max_timestamp_ - cur_max_timestamp_;
       DVLOG(1) << "stream " << stream_id_
                << ": Net.QuicSession.HeadersHOLBlockedTime "
                << delta.ToMilliseconds();