Implement a new flow event API that allows binding flow events and regular events.

base/debug/task_annotator.cc

 // Copyright 2014 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 "base/debug/task_annotator.h"
 
 #include "base/debug/alias.h"
 #include "base/pending_task.h"
 #include "base/trace_event/trace_event.h"
 #include "base/tracked_objects.h"
 
 namespace base {
 namespace debug {
 
 TaskAnnotator::TaskAnnotator() {
 }
 
 TaskAnnotator::~TaskAnnotator() {
 }
 
 void TaskAnnotator::DidQueueTask(const char* queue_function,
                                  const PendingTask& pending_task) {
+  TRACE_EVENT_WITH_FLOW0("toplevel", "TaskAnnotator::DidQueueTask",
+                         TRACE_ID_MANGLE(GetTaskTraceID(pending_task)),
+                         TRACE_EVENT_FLAG_FLOW_OUT);
   TRACE_EVENT_FLOW_BEGIN0(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
                           queue_function,
                           TRACE_ID_MANGLE(GetTaskTraceID(pending_task)));
 }
 
 void TaskAnnotator::RunTask(const char* queue_function,
                             const char* run_function,
                             const PendingTask& pending_task) {
   tracked_objects::TaskStopwatch stopwatch;
   stopwatch.Start();
   tracked_objects::Duration queue_duration =
       stopwatch.StartTime() - pending_task.EffectiveTimePosted();
 
+  // When tracing memory for posted tasks it's more valuable to attribute the
+  // memory allocations to the source function than generically to the task
+  // runner.
+  TRACE_EVENT_WITH_MEMORY_TAG_WITH_FLOW2(
+      "toplevel", run_function,
+      pending_task.posted_from.function_name(),  // Name for memory tracking.
+      TRACE_ID_MANGLE(GetTaskTraceID(pending_task)), TRACE_EVENT_FLAG_FLOW_IN,
+      "src_file", pending_task.posted_from.file_name(), "src_func",
+      pending_task.posted_from.function_name());
+
   TRACE_EVENT_FLOW_END1(TRACE_DISABLED_BY_DEFAULT("toplevel.flow"),
                         queue_function,
                         TRACE_ID_MANGLE(GetTaskTraceID(pending_task)),
-                        "queue_duration",
-                        queue_duration.InMilliseconds());
-
-  // When tracing memory for posted tasks it's more valuable to attribute the
-  // memory allocations to the source function than generically to the task
-  // runner.
-  TRACE_EVENT_WITH_MEMORY_TAG2(
-      "toplevel",
-      run_function,
-      pending_task.posted_from.function_name(),  // Name for memory tracking.
-      "src_file",
-      pending_task.posted_from.file_name(),
-      "src_func",
-      pending_task.posted_from.function_name());
+                        "queue_duration", queue_duration.InMilliseconds());
 
   // Before running the task, store the program counter where it was posted
   // and deliberately alias it to ensure it is on the stack if the task
   // crashes. Be careful not to assume that the variable itself will have the
   // expected value when displayed by the optimizer in an optimized build.
   // Look at a memory dump of the stack.
   const void* program_counter = pending_task.posted_from.program_counter();
   debug::Alias(&program_counter);
 
   pending_task.task.Run();
 
   stopwatch.Stop();
   tracked_objects::ThreadData::TallyRunOnNamedThreadIfTracking(
       pending_task, stopwatch);
 }
 
 uint64 TaskAnnotator::GetTaskTraceID(const PendingTask& task) const {
   return (static_cast<uint64>(task.sequence_num) << 32) |
          ((static_cast<uint64>(reinterpret_cast<intptr_t>(this)) << 32) >> 32);
 }
 
 }  // namespace debug
 }  // namespace base