Add toString() for SequentialExecutor's worker runnable

RELNOTES=n/a

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=320760882

Author: clm

android/guava-tests/test/com/google/common/util/concurrent/SequentialExecutorTest.java

@@ -351,10 +351,15 @@ public void run() {
   }
 
   public void testToString() {
-    Executor delegate =
+    final Runnable[] currentTask = new Runnable[1];
+    final Executor delegate =
         new Executor() {
           @Override
-          public void execute(Runnable task) {}
+          public void execute(Runnable task) {
+            currentTask[0] = task;
+            task.run();
+            currentTask[0] = null;
+          }
 
           @Override
           public String toString() {
@@ -365,5 +370,19 @@ public String toString() {
     Executor sequential2 = newSequentialExecutor(delegate);
     assertThat(sequential1.toString()).contains("theDelegate");
     assertThat(sequential1.toString()).isNotEqualTo(sequential2.toString());
+    final String[] whileRunningToString = new String[1];
+    sequential1.execute(
+        new Runnable() {
+          @Override
+          public void run() {
+            whileRunningToString[0] = "" + currentTask[0];
+          }
+
+          @Override
+          public String toString() {
+            return "my runnable's toString";
+          }
+        });
+    assertThat(whileRunningToString[0]).contains("my runnable's toString");
   }
 }

android/guava/src/com/google/common/util/concurrent/SequentialExecutor.java

@@ -120,6 +120,11 @@ public void execute(final Runnable task) {
             public void run() {
               task.run();
             }
+
+            @Override
+            public String toString() {
+              return task.toString();
+            }
           };
       queue.add(submittedTask);
       workerRunningState = QUEUING;
@@ -165,6 +170,8 @@ public void run() {
 
   /** Worker that runs tasks from {@link #queue} until it is empty. */
   private final class QueueWorker implements Runnable {
+    Runnable task;
+
     @Override
     public void run() {
       try {
@@ -196,7 +203,6 @@ private void workOnQueue() {
       boolean hasSetRunning = false;
       try {
         while (true) {
-          Runnable task;
           synchronized (queue) {
             // Choose whether this thread will run or not after acquiring the lock on the first
             // iteration
@@ -227,6 +233,8 @@ private void workOnQueue() {
             task.run();
           } catch (RuntimeException e) {
             log.log(Level.SEVERE, "Exception while executing runnable " + task, e);
+          } finally {
+            task = null;
           }
         }
       } finally {
@@ -238,6 +246,16 @@ private void workOnQueue() {
         }
       }
     }
+
+    @SuppressWarnings("GuardedBy")
+    @Override
+    public String toString() {
+      Runnable currentlyRunning = task;
+      if (currentlyRunning != null) {
+        return "SequentialExecutorWorker{running=" + currentlyRunning + "}";
+      }
+      return "SequentialExecutorWorker{state=" + workerRunningState + "}";
+    }
   }
 
   @Override

guava-tests/test/com/google/common/util/concurrent/SequentialExecutorTest.java

@@ -351,10 +351,15 @@ public void run() {
   }
 
   public void testToString() {
-    Executor delegate =
+    final Runnable[] currentTask = new Runnable[1];
+    final Executor delegate =
         new Executor() {
           @Override
-          public void execute(Runnable task) {}
+          public void execute(Runnable task) {
+            currentTask[0] = task;
+            task.run();
+            currentTask[0] = null;
+          }
 
           @Override
           public String toString() {
@@ -365,5 +370,19 @@ public String toString() {
     Executor sequential2 = newSequentialExecutor(delegate);
     assertThat(sequential1.toString()).contains("theDelegate");
     assertThat(sequential1.toString()).isNotEqualTo(sequential2.toString());
+    final String[] whileRunningToString = new String[1];
+    sequential1.execute(
+        new Runnable() {
+          @Override
+          public void run() {
+            whileRunningToString[0] = "" + currentTask[0];
+          }
+
+          @Override
+          public String toString() {
+            return "my runnable's toString";
+          }
+        });
+    assertThat(whileRunningToString[0]).contains("my runnable's toString");
   }
 }

guava/src/com/google/common/util/concurrent/SequentialExecutor.java

@@ -120,6 +120,11 @@ public void execute(final Runnable task) {
             public void run() {
               task.run();
             }
+
+            @Override
+            public String toString() {
+              return task.toString();
+            }
           };
       queue.add(submittedTask);
       workerRunningState = QUEUING;
@@ -165,6 +170,8 @@ public void run() {
 
   /** Worker that runs tasks from {@link #queue} until it is empty. */
   private final class QueueWorker implements Runnable {
+    Runnable task;
+
     @Override
     public void run() {
       try {
@@ -196,7 +203,6 @@ private void workOnQueue() {
       boolean hasSetRunning = false;
       try {
         while (true) {
-          Runnable task;
           synchronized (queue) {
             // Choose whether this thread will run or not after acquiring the lock on the first
             // iteration
@@ -227,6 +233,8 @@ private void workOnQueue() {
             task.run();
           } catch (RuntimeException e) {
             log.log(Level.SEVERE, "Exception while executing runnable " + task, e);
+          } finally {
+            task = null;
           }
         }
       } finally {
@@ -238,6 +246,16 @@ private void workOnQueue() {
         }
       }
     }
+
+    @SuppressWarnings("GuardedBy")
+    @Override
+    public String toString() {
+      Runnable currentlyRunning = task;
+      if (currentlyRunning != null) {
+        return "SequentialExecutorWorker{running=" + currentlyRunning + "}";
+      }
+      return "SequentialExecutorWorker{state=" + workerRunningState + "}";
+    }
   }
 
   @Override