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

ios/web/web_thread_impl.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 "ios/web/web_thread_impl.h"
 
 #include <string>
 #include <utility>
 
 #include "base/atomicops.h"
@@ skipping 31 matching lines @@
 }
 
 // An implementation of SingleThreadTaskRunner to be used in conjunction
 // with WebThread.
 class WebThreadTaskRunner : public base::SingleThreadTaskRunner {
  public:
   explicit WebThreadTaskRunner(WebThread::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 WebThread::PostDelayedTask(id_, from_here, task, delay);
+    return WebThread::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 WebThread::PostNonNestableDelayedTask(id_, from_here, task, delay);
+    return WebThread::PostNonNestableDelayedTask(id_, from_here,
+                                                 std::move(task), delay);
   }
 
   bool RunsTasksOnCurrentThread() const override {
     return WebThread::CurrentlyOn(id_);
   }
 
  protected:
   ~WebThreadTaskRunner() override {}
 
  private:
@@ skipping 212 matching lines @@
   for (int i = identifier_ + 1; i < ID_COUNT; ++i) {
     DCHECK(!globals.threads[i])
         << "Threads must be listed in the reverse order that they die";
   }
 #endif
 }
 
 // static
 bool WebThreadImpl::PostTaskHelper(WebThread::ID identifier,
                                    const tracked_objects::Location& from_here,
-                                   const base::Closure& task,
+                                   base::Closure task,
                                    base::TimeDelta delay,
                                    bool nestable) {
   DCHECK(identifier >= 0 && 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.
   // 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.
   WebThread::ID current_thread = ID_COUNT;
   bool target_thread_outlives_current =
       GetCurrentThreadIdentifier(&current_thread) &&
       current_thread >= identifier;
 
   WebThreadGlobals& globals = g_globals.Get();
   if (!target_thread_outlives_current)
     globals.lock.Acquire();
 
   base::MessageLoop* message_loop =
       globals.threads[identifier] ? globals.threads[identifier]->message_loop()
                                   : nullptr;
   if (message_loop) {
     if (nestable) {
-      message_loop->task_runner()->PostDelayedTask(from_here, task, delay);
+      message_loop->task_runner()->PostDelayedTask(from_here, std::move(task),
+                                                   delay);
     } else {
-      message_loop->task_runner()->PostNonNestableDelayedTask(from_here, task,
-                                                              delay);
+      message_loop->task_runner()->PostNonNestableDelayedTask(
+          from_here, std::move(task), delay);
     }
   }
 
   if (!target_thread_outlives_current)
     globals.lock.Release();
 
   return !!message_loop;
 }
 
 // static
 bool WebThread::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 WebThread::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 WebThread::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
 base::SequencedWorkerPool* WebThread::GetBlockingPool() {
   return g_globals.Get().blocking_pool.get();
 }
 
 // static
 bool WebThread::IsThreadInitialized(ID identifier) {
   if (g_globals == nullptr)
@@ skipping 37 matching lines @@
   WebThreadGlobals& globals = g_globals.Get();
   base::AutoLock lock(globals.lock);
   DCHECK(identifier >= 0 && identifier < ID_COUNT);
   return globals.threads[identifier] &&
          globals.threads[identifier]->message_loop();
 }
 
 // static
 bool WebThread::PostTask(ID identifier,
                          const tracked_objects::Location& from_here,
-                         const base::Closure& task) {
-  return WebThreadImpl::PostTaskHelper(identifier, from_here, task,
+                         base::Closure task) {
+  return WebThreadImpl::PostTaskHelper(identifier, from_here, std::move(task),
                                        base::TimeDelta(), true);
 }
 
 // static
 bool WebThread::PostDelayedTask(ID identifier,
                                 const tracked_objects::Location& from_here,
-                                const base::Closure& task,
+                                base::Closure task,
                                 base::TimeDelta delay) {
-  return WebThreadImpl::PostTaskHelper(identifier, from_here, task, delay,
-                                       true);
+  return WebThreadImpl::PostTaskHelper(identifier, from_here, std::move(task),
+                                       delay, true);
 }
 
 // static
 bool WebThread::PostNonNestableTask(ID identifier,
                                     const tracked_objects::Location& from_here,
-                                    const base::Closure& task) {
-  return WebThreadImpl::PostTaskHelper(identifier, from_here, task,
+                                    base::Closure task) {
+  return WebThreadImpl::PostTaskHelper(identifier, from_here, std::move(task),
                                        base::TimeDelta(), false);
 }
 
 // static
 bool WebThread::PostNonNestableDelayedTask(
     ID identifier,
     const tracked_objects::Location& from_here,
-    const base::Closure& task,
+    base::Closure task,
     base::TimeDelta delay) {
-  return WebThreadImpl::PostTaskHelper(identifier, from_here, task, delay,
-                                       false);
+  return WebThreadImpl::PostTaskHelper(identifier, from_here, std::move(task),
+                                       delay, false);
 }
 
 // static
 bool WebThread::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 29 matching lines @@
   AtomicWord* storage =
       reinterpret_cast<AtomicWord*>(&globals.thread_delegates[identifier]);
   AtomicWord old_pointer = base::subtle::NoBarrier_AtomicExchange(
       storage, reinterpret_cast<AtomicWord>(delegate));
 
   // This catches registration when previously registered.
   DCHECK(!delegate || !old_pointer);
 }
 
 }  // namespace web