Separate the create and start phases in DelayedTaskManager.

base/task_scheduler/delayed_task_manager.cc

Index: base/task_scheduler/delayed_task_manager.cc
diff --git a/base/task_scheduler/delayed_task_manager.cc b/base/task_scheduler/delayed_task_manager.cc
index 420f8937f8bac38d0a99b21961f672964978dfa6..f40f3296a58bd8fb64a3d23365ee8bb4d32afb4c 100644
--- a/base/task_scheduler/delayed_task_manager.cc
+++ b/base/task_scheduler/delayed_task_manager.cc
@@ -4,7 +4,7 @@
 
 #include "base/task_scheduler/delayed_task_manager.h"
 
-#include <utility>
+#include <algorithm>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ -14,27 +14,51 @@
 namespace base {
 namespace internal {
 
-DelayedTaskManager::DelayedTaskManager(
-    scoped_refptr<TaskRunner> service_thread_task_runner)
-    : service_thread_task_runner_(std::move(service_thread_task_runner)) {
-  DCHECK(service_thread_task_runner_);
-}
-
+DelayedTaskManager::DelayedTaskManager() = default;
 DelayedTaskManager::~DelayedTaskManager() = default;
 
+void DelayedTaskManager::Start(
+    scoped_refptr<TaskRunner> service_thread_task_runner) {
+  AutoSchedulerLock auto_lock(lock_);
+  DCHECK(service_thread_task_runner);
+  DCHECK(!service_thread_task_runner_);
+  service_thread_task_runner_ = std::move(service_thread_task_runner);
+
+  const TimeTicks now = TimeTicks::Now();
+  for (auto& task_and_callback : tasks_added_before_start_) {
+    const TimeDelta delay =
+        std::max(TimeDelta(), task_and_callback.first->delayed_run_time - now);
+    service_thread_task_runner_->PostDelayedTask(
+        FROM_HERE,
+        BindOnce(std::move(task_and_callback.second),
+                 Passed(std::move(task_and_callback.first))),
+        delay);
+  }
+  tasks_added_before_start_.clear();
+}
+
 void DelayedTaskManager::AddDelayedTask(
     std::unique_ptr<Task> task,
-    const PostTaskNowCallback& post_task_now_callback) {
+    PostTaskNowCallback post_task_now_callback) {
   DCHECK(task);
   DCHECK(task->task);
 
   const TimeDelta delay = task->delay;
   DCHECK(!delay.is_zero());
 
-  // TODO(fdoray): Use |task->delayed_run_time| on the service thread
-  // MessageLoop rather than recomputing it from |delay|.
-  service_thread_task_runner_->PostDelayedTask(
-      FROM_HERE, Bind(post_task_now_callback, Passed(std::move(task))), delay);
+  AutoSchedulerLock auto_lock(lock_);
+
+  if (service_thread_task_runner_) {
+    // TODO(fdoray): Use |task->delayed_run_time| on the service thread
+    // MessageLoop rather than recomputing it from |delay|.
+    service_thread_task_runner_->PostDelayedTask(
+        FROM_HERE,
+        BindOnce(std::move(post_task_now_callback), Passed(std::move(task))),
+        delay);
+  } else {
+    tasks_added_before_start_.push_back(
+        {std::move(task), std::move(post_task_now_callback)});
+  }
 }
 
 }  // namespace internal