Revert of [heap] Cancel tasks before tearing down the heap.

src/cancelable-task.cc

Index: src/cancelable-task.cc
diff --git a/src/cancelable-task.cc b/src/cancelable-task.cc
index 852f4ffda806bbc2266cd61ee64de2a5f421f419..defbb44775a8c1f64b8eedac62ea21b8376eacd1 100644
--- a/src/cancelable-task.cc
+++ b/src/cancelable-task.cc
@@ -26,20 +26,14 @@
   }
 }
 
-CancelableTaskManager::CancelableTaskManager()
-    : task_id_counter_(0), canceled_(false) {}
+CancelableTaskManager::CancelableTaskManager() : task_id_counter_(0) {}
 
 uint32_t CancelableTaskManager::Register(Cancelable* task) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   uint32_t id = ++task_id_counter_;
   // The loop below is just used when task_id_counter_ overflows.
   while (cancelable_tasks_.count(id) > 0) ++id;
-  if (canceled_) {
-    bool successfully_canceled_task = task->Cancel();
-    CHECK(successfully_canceled_task);
-  } else {
-    cancelable_tasks_[id] = task;
-  }
+  cancelable_tasks_[id] = task;
   return id;
 }
 
@@ -75,7 +69,6 @@
   // of canceling we wait for the background tasks that have already been
   // started.
   base::LockGuard<base::Mutex> guard(&mutex_);
-  canceled_ = true;
 
   // Cancelable tasks could be running or could potentially register new
   // tasks, requiring a loop here.