Adding instrumentation to locate the source of jankiness.

net/disk_cache/blockfile/in_flight_backend_io.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/blockfile/in_flight_backend_io.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
+#include "base/profiler/scoped_profile.h"
 #include "base/single_thread_task_runner.h"
 #include "net/base/net_errors.h"
 #include "net/disk_cache/blockfile/backend_impl.h"
 #include "net/disk_cache/blockfile/entry_impl.h"
 #include "net/disk_cache/blockfile/histogram_macros.h"
 
 // Provide a BackendImpl object to macros from histogram_macros.h.
 #define CACHE_UMA_BACKEND_IMPL_OBJ backend_
 
 namespace disk_cache {
@@ skipping 36 matching lines @@
 void BackendIO::OnDone(bool cancel) {
   if (IsEntryOperation()) {
     CACHE_UMA(TIMES, "TotalIOTime", 0, ElapsedTime());
   }
 
   if (!ReturnsEntry())
     return;
 
   if (result() == net::OK) {
     static_cast<EntryImpl*>(*entry_ptr_)->OnEntryCreated(backend_);
-    if (cancel)
+    if (cancel) {
+      // TODO(vadimt): Remove ScopedProfile below once crbug.com/422516 is
+      // fixed.
+      tracked_objects::ScopedProfile tracking_profile(
+          FROM_HERE_WITH_EXPLICIT_FUNCTION("422516 BackendIO::OnDone"));
+
       (*entry_ptr_)->Close();
+    }
   }
 }
 
 bool BackendIO::IsEntryOperation() {
   return operation_ > OP_MAX_BACKEND;
 }
 
 // Runs on the background thread.
 void BackendIO::ReferenceEntry() {
   entry_->AddRef();
@@ skipping 410 matching lines @@
 
 void InFlightBackendIO::WaitForPendingIO() {
   InFlightIO::WaitForPendingIO();
 }
 
 void InFlightBackendIO::OnOperationComplete(BackgroundIO* operation,
                                             bool cancel) {
   BackendIO* op = static_cast<BackendIO*>(operation);
   op->OnDone(cancel);
 
-  if (!op->callback().is_null() && (!cancel || op->IsEntryOperation()))
+  if (!op->callback().is_null() && (!cancel || op->IsEntryOperation())) {
+    // TODO(vadimt): Remove ScopedProfile below once crbug.com/422516 is fixed.
+    tracked_objects::ScopedProfile tracking_profile(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "422516 InFlightBackendIO::OnOperationComplete"));
+
     op->callback().Run(op->result());
+  }
 }
 
 void InFlightBackendIO::PostOperation(BackendIO* operation) {
   background_thread_->PostTask(
       FROM_HERE, base::Bind(&BackendIO::ExecuteOperation, operation));
   OnOperationPosted(operation);
 }
 
 base::WeakPtr<InFlightBackendIO> InFlightBackendIO::GetWeakPtr() {
   return ptr_factory_.GetWeakPtr();
 }
 
 }  // namespace