Adding instrumentation to locate the source of jankiness.

net/spdy/spdy_session.cc

Index: net/spdy/spdy_session.cc
diff --git a/net/spdy/spdy_session.cc b/net/spdy/spdy_session.cc
index d5f04adb3d65409ad238fc47fd9fec6838e08315..6afa427f0ab0b57ebcc6147b1522164c09b06602 100644
--- a/net/spdy/spdy_session.cc
+++ b/net/spdy/spdy_session.cc
@@ -16,6 +16,7 @@
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/metrics/stats_counters.h"
+#include "base/profiler/scoped_profile.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -1336,6 +1337,11 @@ void SpdySession::EnqueueResetStreamFrame(SpdyStreamId stream_id,
 }
 
 void SpdySession::PumpReadLoop(ReadState expected_read_state, int result) {
+  // TODO(vadimt): Remove ScopedProfile below once crbug.com/418183 is fixed.
+  tracked_objects::ScopedProfile tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "418183 DoReadCallback => SpdySession::PumpReadLoop"));
+
   CHECK(!in_io_loop_);
   if (availability_state_ == STATE_DRAINING) {
     return;