[task-runner] fix `std::move` on const values (#1474)

There is an issue in `TaskRunner` that it declares `Task<void>` as a
const parameter in interfaces (e.g. `void TaskRunner::Post(const
Task<void> aTask)`). In the implementation it `std::move`s the `aTask`
and pushed it into an STL container. This `std::move` on the const
value doesn't lead to the move constructor of `Task<void>` which may
have better performance. It leads to the copy constructor instead. To
fix this, we need to make the `aTask` a non-const parameter.

2 files changed, 6 insertions, 6 deletions

diff --git a/src/common/task_runner.cpp b/src/common/task_runner.cpp
index 75a0cb56..4ee0328d 100644
--- a/src/common/task_runner.cpp
+++ b/src/common/task_runner.cpp
@@ -70,12 +70,12 @@ TaskRunner::~TaskRunner(void)
     }
 }
 
-void TaskRunner::Post(const Task<void> aTask)
+void TaskRunner::Post(Task<void> aTask)
 {
     Post(Milliseconds::zero(), std::move(aTask));
 }
 
-void TaskRunner::Post(Milliseconds aDelay, const Task<void> aTask)
+void TaskRunner::Post(Milliseconds aDelay, Task<void> aTask)
 {
     PushTask(aDelay, std::move(aTask));
 }
@@ -129,7 +129,7 @@ void TaskRunner::Process(const MainloopContext &aMainloop)
     PopTasks();
 }
 
-void TaskRunner::PushTask(Milliseconds aDelay, const Task<void> aTask)
+void TaskRunner::PushTask(Milliseconds aDelay, Task<void> aTask)
 {
     ssize_t                     rval;
     const uint8_t               kOne = 1;
diff --git a/src/common/task_runner.hpp b/src/common/task_runner.hpp
index f9a9a730..fe81e9c1 100644
--- a/src/common/task_runner.hpp
+++ b/src/common/task_runner.hpp
@@ -83,7 +83,7 @@ public:
      * @param[in] aTask  The task to be executed.
      *
      */
-    void Post(const Task<void> aTask);
+    void Post(Task<void> aTask);
 
     /**
      * This method posts a task to the task runner and returns immediately.
@@ -94,7 +94,7 @@ public:
      * @param[in] aTask   The task to be executed.
      *
      */
-    void Post(Milliseconds aDelay, const Task<void> aTask);
+    void Post(Milliseconds aDelay, Task<void> aTask);
 
     /**
      * This method posts a task and waits for the completion of the task.
@@ -154,7 +154,7 @@ private:
         Task<void>   mTask;
     };
 
-    void PushTask(Milliseconds aDelay, const Task<void> aTask);
+    void PushTask(Milliseconds aDelay, Task<void> aTask);
     void PopTasks(void);
 
     // The event fds which are used to wakeup the mainloop