QUIC - Added histogram to track the number of total

blocked frames sent/received when a connection is finished.

Histogram name: Net.QuicSession.BlockedFrames.Received and
                Net.QuicSession.BlockedFrames.Sent.

R=asvitkine@chromium.org, rch@chromium.org

Review URL: https://codereview.chromium.org/669793003

Cr-Commit-Position: refs/heads/master@{#300739}

net/quic/quic_connection_logger.cc

@@ -339,6 +339,8 @@ QuicConnectionLogger::QuicConnectionLogger(QuicSession* session,
       num_incorrect_connection_ids_(0),
       num_undecryptable_packets_(0),
       num_duplicate_packets_(0),
+      num_blocked_frames_received_(0),
+      num_blocked_frames_sent_(0),
       connection_description_(GetConnectionDescriptionString()) {
 }
 
@@ -355,6 +357,10 @@ QuicConnectionLogger::~QuicConnectionLogger() {
                        num_undecryptable_packets_);
   UMA_HISTOGRAM_COUNTS("Net.QuicSession.DuplicatePacketsReceived",
                        num_duplicate_packets_);
+  UMA_HISTOGRAM_COUNTS("Net.QuicSession.BlockedFrames.Received",
+                       num_blocked_frames_received_);
+  UMA_HISTOGRAM_COUNTS("Net.QuicSession.BlockedFrames.Sent",
+                       num_blocked_frames_sent_);
 
   if (num_frames_received_ > 0) {
     int duplicate_stream_frame_per_thousand =
@@ -442,6 +448,7 @@ void QuicConnectionLogger::OnFrameAddedToPacket(const QuicFrame& frame) {
                      frame.window_update_frame));
       break;
     case BLOCKED_FRAME:
+      ++num_blocked_frames_sent_;
       net_log_.AddEvent(
           NetLog::TYPE_QUIC_SESSION_BLOCKED_FRAME_SENT,
           base::Bind(&NetLogQuicBlockedFrameCallback,
@@ -636,6 +643,7 @@ void QuicConnectionLogger::OnWindowUpdateFrame(
 }
 
 void QuicConnectionLogger::OnBlockedFrame(const QuicBlockedFrame& frame) {
+  ++num_blocked_frames_received_;
   net_log_.AddEvent(
       NetLog::TYPE_QUIC_SESSION_BLOCKED_FRAME_RECEIVED,
       base::Bind(&NetLogQuicBlockedFrameCallback, &frame));

net/quic/quic_connection_logger.h

@@ -151,6 +151,10 @@ class NET_EXPORT_PRIVATE QuicConnectionLogger
   int num_undecryptable_packets_;
   // Count of the number of duplicate packets received.
   int num_duplicate_packets_;
+  // Count of the number of BLOCKED frames received.
+  int num_blocked_frames_received_;
+  // Count of the number of BLOCKED frames sent.
+  int num_blocked_frames_sent_;
   // Vector of inital packets status' indexed by packet sequence numbers, where
   // false means never received.  Zero is not a valid packet sequence number, so
   // that offset is never used, and we'll track 150 packets.

tools/metrics/histograms/histograms.xml

@@ -17268,6 +17268,22 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicSession.BlockedFrames.Received">
+  <owner>rtenneti@chromium.org</owner>
+  <summary>
+    The number of BLOCKED frames recevied by a QuicSession when the session is
+    closed.
+  </summary>
+</histogram>
+
+<histogram name="Net.QuicSession.BlockedFrames.Sent">
+  <owner>rtenneti@chromium.org</owner>
+  <summary>
+    The number of BLOCKED frames sent by a QuicSession when the session is
+    closed.
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicSession.ClosedDuringInitializeSession">
   <owner>rch@chromium.org</owner>
   <summary>