2.x: Add support for concurrently inserting actions while advancing time (#3648)

* 2.x: Adding support for concurrently inserting actions while advancing time

* Removing the unit test proving the thread safety of
a BlockingPriorityQueue.

Author: bcorne

src/main/java/io/reactivex/schedulers/TestScheduler.java

@@ -14,6 +14,7 @@
 package io.reactivex.schedulers;
 
 import java.util.*;
+import java.util.concurrent.PriorityBlockingQueue;
 import java.util.concurrent.TimeUnit;
 
 import io.reactivex.Scheduler;
@@ -28,7 +29,7 @@
  */
 public final class TestScheduler extends Scheduler {
     /** The ordered queue for the runnable tasks. */
-    private final Queue<TimedRunnable> queue = new PriorityQueue<TimedRunnable>(11);
+    private final Queue<TimedRunnable> queue = new PriorityBlockingQueue<TimedRunnable>(11);
     /** The per-scheduler global order counter. */
     long counter;
 
@@ -61,7 +62,7 @@ public int compareTo(TimedRunnable o) {
     }
 
     // Storing time in nanoseconds internally.
-    private long time;
+    private volatile long time;
 
     @Override
     public long now(TimeUnit unit) {

src/test/java/io/reactivex/schedulers/TestSchedulerTest.java

@@ -14,9 +14,13 @@
 package io.reactivex.schedulers;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 import static org.mockito.Matchers.anyLong;
 import static org.mockito.Mockito.*;
 
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.CyclicBarrier;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -216,4 +220,5 @@ public void run() {
             inner.dispose();
         }
     }
+
 }