Revert of Remove the code to store and load QUIC server configs in the disk cache.

net/quic/chromium/quic_chromium_client_session.cc

Index: net/quic/chromium/quic_chromium_client_session.cc
diff --git a/net/quic/chromium/quic_chromium_client_session.cc b/net/quic/chromium/quic_chromium_client_session.cc
index cfac1d3ba6053bdc7bf088ad023219faf48759b9..ba6c37c3c5faa43607fac245ee8ce90dc5dfccfb 100644
--- a/net/quic/chromium/quic_chromium_client_session.cc
+++ b/net/quic/chromium/quic_chromium_client_session.cc
@@ -375,8 +375,24 @@
           round_trip_handshakes, 1, 3, 4);
     }
   }
-
   const QuicConnectionStats stats = connection()->GetStats();
+  if (server_info_ && stats.min_rtt_us > 0) {
+    base::TimeTicks wait_for_data_start_time =
+        server_info_->wait_for_data_start_time();
+    base::TimeTicks wait_for_data_end_time =
+        server_info_->wait_for_data_end_time();
+    if (!wait_for_data_start_time.is_null() &&
+        !wait_for_data_end_time.is_null()) {
+      base::TimeDelta wait_time =
+          wait_for_data_end_time - wait_for_data_start_time;
+      const base::HistogramBase::Sample kMaxWaitToRtt = 1000;
+      base::HistogramBase::Sample wait_to_rtt =
+          static_cast<base::HistogramBase::Sample>(
+              100 * wait_time.InMicroseconds() / stats.min_rtt_us);
+      UMA_HISTOGRAM_CUSTOM_COUNTS("Net.QuicServerInfo.WaitForDataReadyToRtt",
+                                  wait_to_rtt, 1, kMaxWaitToRtt, 50);
+    }
+  }
 
   // The MTU used by QUIC is limited to a fairly small set of predefined values
   // (initial values and MTU discovery values), but does not fare well when
@@ -841,6 +857,21 @@
     UMA_HISTOGRAM_TIMES(
         "Net.QuicSession.HandshakeConfirmedTime",
         connect_timing_.connect_end - connect_timing_.connect_start);
+
+    if (server_info_) {
+      // TODO(rtenneti): Should we delete this histogram?
+      // Track how long it has taken to finish handshake once we start waiting
+      // for reading of QUIC server information from disk cache. We could use
+      // this data to compare total time taken if we were to cancel the disk
+      // cache read vs waiting for the read to complete.
+      base::TimeTicks wait_for_data_start_time =
+          server_info_->wait_for_data_start_time();
+      if (!wait_for_data_start_time.is_null()) {
+        UMA_HISTOGRAM_TIMES(
+            "Net.QuicServerInfo.WaitForDataReady.HandshakeConfirmedTime",
+            base::TimeTicks::Now() - wait_for_data_start_time);
+      }
+    }
     // Track how long it has taken to finish handshake after we have finished
     // DNS host resolution.
     if (!connect_timing_.dns_end.is_null()) {
@@ -855,6 +886,8 @@
       ++it;
       observer->OnCryptoHandshakeConfirmed();
     }
+    if (server_info_)
+      server_info_->OnExternalCacheHit();
   }
   QuicSpdySession::OnCryptoHandshakeEvent(event);
 }