Pass Callback to TaskRunner by value and consume it on invocation (1)

content/browser/browser_thread_impl.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 "content/browser/browser_thread_impl.h"
 
 #include <string>
 #include <utility>
 
 #include "base/atomicops.h"
@@ skipping 44 matching lines @@
 // with BrowserThread.
 // TODO(gab): Consider replacing this with |g_globals->task_runners| -- only
 // works if none are requested before starting the threads.
 class BrowserThreadTaskRunner : public base::SingleThreadTaskRunner {
  public:
   explicit BrowserThreadTaskRunner(BrowserThread::ID identifier)
       : id_(identifier) {}
 
   // SingleThreadTaskRunner implementation.
   bool PostDelayedTask(const tracked_objects::Location& from_here,
-                       const base::Closure& task,
+                       base::Closure task,
                        base::TimeDelta delay) override {
-    return BrowserThread::PostDelayedTask(id_, from_here, task, delay);
+    return BrowserThread::PostDelayedTask(id_, from_here, std::move(task),
+                                          delay);
   }
 
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
-                                  const base::Closure& task,
+                                  base::Closure task,
                                   base::TimeDelta delay) override {
-    return BrowserThread::PostNonNestableDelayedTask(id_, from_here, task,
-                                                     delay);
+    return BrowserThread::PostNonNestableDelayedTask(id_, from_here,
+                                                     std::move(task), delay);
   }
 
   bool RunsTasksOnCurrentThread() const override {
     return BrowserThread::CurrentlyOn(id_);
   }
 
  protected:
   ~BrowserThreadTaskRunner() override {}
 
  private:
@@ skipping 397 matching lines @@
   // succeed to post to B. This is pretty much the only observable difference
   // between a redirected thread and a real one and is one we're willing to live
   // with for this experiment. TODO(gab): fix this before enabling the
   // experiment by default on trunk, http://crbug.com/653916.
 }
 
 // static
 bool BrowserThreadImpl::PostTaskHelper(
     BrowserThread::ID identifier,
     const tracked_objects::Location& from_here,
-    const base::Closure& task,
+    base::Closure task,
     base::TimeDelta delay,
     bool nestable) {
   DCHECK_GE(identifier, 0);
   DCHECK_LT(identifier, ID_COUNT);
   // Optimization: to avoid unnecessary locks, we listed the ID enumeration in
   // order of lifetime.  So no need to lock if we know that the target thread
   // outlives current thread as that implies the current thread only ever sees
   // the target thread in its RUNNING state.
   // Note: since the array is so small, ok to loop instead of creating a map,
   // which would require a lock because std::map isn't thread safe, defeating
   // the whole purpose of this optimization.
   BrowserThread::ID current_thread = ID_COUNT;
   bool target_thread_outlives_current =
       GetCurrentThreadIdentifier(&current_thread) &&
       current_thread >= identifier;
 
   BrowserThreadGlobals& globals = g_globals.Get();
   if (!target_thread_outlives_current)
     globals.lock.Acquire();
 
   const bool accepting_tasks =
       globals.states[identifier] == BrowserThreadState::RUNNING;
   if (accepting_tasks) {
     base::SingleThreadTaskRunner* task_runner =
         globals.task_runners[identifier].get();
     DCHECK(task_runner);
     if (nestable) {
-      task_runner->PostDelayedTask(from_here, task, delay);
+      task_runner->PostDelayedTask(from_here, std::move(task), delay);
     } else {
-      task_runner->PostNonNestableDelayedTask(from_here, task, delay);
+      task_runner->PostNonNestableDelayedTask(from_here, std::move(task),
+                                              delay);
     }
   }
 
   if (!target_thread_outlives_current)
     globals.lock.Release();
 
   return accepting_tasks;
 }
 
 // static
 bool BrowserThread::PostBlockingPoolTask(
     const tracked_objects::Location& from_here,
-    const base::Closure& task) {
-  return g_globals.Get().blocking_pool->PostWorkerTask(from_here, task);
+    base::Closure task) {
+  return g_globals.Get().blocking_pool->PostWorkerTask(from_here,
+                                                       std::move(task));
 }
 
 // static
 bool BrowserThread::PostBlockingPoolTaskAndReply(
     const tracked_objects::Location& from_here,
     base::Closure task,
     base::Closure reply) {
   return g_globals.Get().blocking_pool->PostTaskAndReply(
       from_here, std::move(task), std::move(reply));
 }
 
 // static
 bool BrowserThread::PostBlockingPoolSequencedTask(
     const std::string& sequence_token_name,
     const tracked_objects::Location& from_here,
-    const base::Closure& task) {
+    base::Closure task) {
   return g_globals.Get().blocking_pool->PostNamedSequencedWorkerTask(
-      sequence_token_name, from_here, task);
+      sequence_token_name, from_here, std::move(task));
 }
 
 // static
 void BrowserThread::PostAfterStartupTask(
     const tracked_objects::Location& from_here,
     const scoped_refptr<base::TaskRunner>& task_runner,
-    const base::Closure& task) {
+    base::Closure task) {
   GetContentClient()->browser()->PostAfterStartupTask(from_here, task_runner,
-                                                      task);
+                                                      std::move(task));
 }
 
 // static
 base::SequencedWorkerPool* BrowserThread::GetBlockingPool() {
   return g_globals.Get().blocking_pool.get();
 }
 
 // static
 bool BrowserThread::IsThreadInitialized(ID identifier) {
   if (g_globals == nullptr)
@@ skipping 39 matching lines @@
   BrowserThreadGlobals& globals = g_globals.Get();
   base::AutoLock lock(globals.lock);
   DCHECK_GE(identifier, 0);
   DCHECK_LT(identifier, ID_COUNT);
   return globals.states[identifier] == BrowserThreadState::RUNNING;
 }
 
 // static
 bool BrowserThread::PostTask(ID identifier,
                              const tracked_objects::Location& from_here,
-                             const base::Closure& task) {
+                             base::Closure task) {
   return BrowserThreadImpl::PostTaskHelper(
-      identifier, from_here, task, base::TimeDelta(), true);
+      identifier, from_here, std::move(task), base::TimeDelta(), true);
 }
 
 // static
 bool BrowserThread::PostDelayedTask(ID identifier,
                                     const tracked_objects::Location& from_here,
-                                    const base::Closure& task,
+                                    base::Closure task,
                                     base::TimeDelta delay) {
-  return BrowserThreadImpl::PostTaskHelper(
-      identifier, from_here, task, delay, true);
+  return BrowserThreadImpl::PostTaskHelper(identifier, from_here,
+                                           std::move(task), delay, true);
 }
 
 // static
 bool BrowserThread::PostNonNestableTask(
     ID identifier,
     const tracked_objects::Location& from_here,
-    const base::Closure& task) {
+    base::Closure task) {
   return BrowserThreadImpl::PostTaskHelper(
-      identifier, from_here, task, base::TimeDelta(), false);
+      identifier, from_here, std::move(task), base::TimeDelta(), false);
 }
 
 // static
 bool BrowserThread::PostNonNestableDelayedTask(
     ID identifier,
     const tracked_objects::Location& from_here,
-    const base::Closure& task,
+    base::Closure task,
     base::TimeDelta delay) {
-  return BrowserThreadImpl::PostTaskHelper(
-      identifier, from_here, task, delay, false);
+  return BrowserThreadImpl::PostTaskHelper(identifier, from_here,
+                                           std::move(task), delay, false);
 }
 
 // static
 bool BrowserThread::PostTaskAndReply(ID identifier,
                                      const tracked_objects::Location& from_here,
                                      base::Closure task,
                                      base::Closure reply) {
   return GetTaskRunnerForThread(identifier)
       ->PostTaskAndReply(from_here, std::move(task), std::move(reply));
 }
@@ skipping 32 matching lines @@
   BrowserThreadDelegateAtomicPtr old_delegate =
       base::subtle::NoBarrier_AtomicExchange(
           &globals.io_thread_delegate,
           reinterpret_cast<BrowserThreadDelegateAtomicPtr>(delegate));
 
   // This catches registration when previously registered.
   DCHECK(!delegate || !old_delegate);
 }
 
 }  // namespace content