Implement some more toString() methods for debugging.

I added these locally while debugging, but they seem potentially generally useful.

RELNOTES=n/a

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=301170647

Author: cpovirk

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

@@ -17,6 +17,7 @@
 package com.google.common.util.concurrent;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.util.concurrent.MoreExecutors.newSequentialExecutor;
 import static com.google.common.util.concurrent.Uninterruptibles.awaitUninterruptibly;
 
 import com.google.common.collect.ImmutableList;
@@ -348,4 +349,21 @@ public void run() {
       assertThat(expected).hasCauseThat().isInstanceOf(RejectedExecutionException.class);
     }
   }
+
+  public void testToString() {
+    Executor delegate =
+        new Executor() {
+          @Override
+          public void execute(Runnable task) {}
+
+          @Override
+          public String toString() {
+            return "theDelegate";
+          }
+        };
+    Executor sequential1 = newSequentialExecutor(delegate);
+    Executor sequential2 = newSequentialExecutor(delegate);
+    assertThat(sequential1.toString()).contains("theDelegate");
+    assertThat(sequential1.toString()).isNotEqualTo(sequential2.toString());
+  }
 }

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

@@ -985,6 +985,11 @@ public void run() {
                   thrownFromDelegate = false;
                   command.run();
                 }
+
+                @Override
+                public String toString() {
+                  return command.toString();
+                }
               });
         } catch (RejectedExecutionException e) {
           if (thrownFromDelegate) {

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

@@ -19,6 +19,7 @@
 import static com.google.common.util.concurrent.SequentialExecutor.WorkerRunningState.QUEUED;
 import static com.google.common.util.concurrent.SequentialExecutor.WorkerRunningState.QUEUING;
 import static com.google.common.util.concurrent.SequentialExecutor.WorkerRunningState.RUNNING;
+import static java.lang.System.identityHashCode;
 
 import com.google.common.annotations.GwtIncompatible;
 import com.google.common.base.Preconditions;
@@ -239,4 +240,9 @@ private void workOnQueue() {
       }
     }
   }
+
+  @Override
+  public String toString() {
+    return "SequentialExecutor@" + identityHashCode(this) + "{" + executor + "}";
+  }
 }

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

@@ -17,6 +17,7 @@
 package com.google.common.util.concurrent;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.util.concurrent.MoreExecutors.newSequentialExecutor;
 import static com.google.common.util.concurrent.Uninterruptibles.awaitUninterruptibly;
 
 import com.google.common.collect.ImmutableList;
@@ -348,4 +349,21 @@ public void run() {
       assertThat(expected).hasCauseThat().isInstanceOf(RejectedExecutionException.class);
     }
   }
+
+  public void testToString() {
+    Executor delegate =
+        new Executor() {
+          @Override
+          public void execute(Runnable task) {}
+
+          @Override
+          public String toString() {
+            return "theDelegate";
+          }
+        };
+    Executor sequential1 = newSequentialExecutor(delegate);
+    Executor sequential2 = newSequentialExecutor(delegate);
+    assertThat(sequential1.toString()).contains("theDelegate");
+    assertThat(sequential1.toString()).isNotEqualTo(sequential2.toString());
+  }
 }

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

@@ -1090,6 +1090,11 @@ public void run() {
                   thrownFromDelegate = false;
                   command.run();
                 }
+
+                @Override
+                public String toString() {
+                  return command.toString();
+                }
               });
         } catch (RejectedExecutionException e) {
           if (thrownFromDelegate) {

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

@@ -19,6 +19,7 @@
 import static com.google.common.util.concurrent.SequentialExecutor.WorkerRunningState.QUEUED;
 import static com.google.common.util.concurrent.SequentialExecutor.WorkerRunningState.QUEUING;
 import static com.google.common.util.concurrent.SequentialExecutor.WorkerRunningState.RUNNING;
+import static java.lang.System.identityHashCode;
 
 import com.google.common.annotations.GwtIncompatible;
 import com.google.common.base.Preconditions;
@@ -239,4 +240,9 @@ private void workOnQueue() {
       }
     }
   }
+
+  @Override
+  public String toString() {
+    return "SequentialExecutor@" + identityHashCode(this) + "{" + executor + "}";
+  }
 }