add queue_statistics to ThreadPool

Signed-off-by: Yilin Chen <sticnarf@gmail.com>

src/pool.rs

@@ -14,7 +14,7 @@ pub use self::builder::{Builder, SchedConfig};
 pub use self::runner::{CloneRunnerBuilder, Runner, RunnerBuilder};
 pub use self::spawn::{build_spawn, Local, Remote};
 
-use crate::queue::{TaskCell, WithExtras};
+use crate::queue::{QueueStatistics, TaskCell, WithExtras};
 use std::mem;
 use std::sync::Mutex;
 use std::thread::JoinHandle;
@@ -48,6 +48,11 @@ impl<T: TaskCell + Send> ThreadPool<T> {
     pub fn remote(&self) -> &Remote<T> {
         &self.remote
     }
+
+    /// Gets the task queue statistics of the thread pool.
+    pub fn queue_statistics(&self) -> QueueStatistics {
+        self.remote.queue_statistics()
+    }
 }
 
 impl<T: TaskCell + Send> Drop for ThreadPool<T> {