Execute DownloadTask threads manually

Instead of using an Executor to run DownloadTasks creates and manages
threads internally.

Also added DownloadThread internal class to better separate the code
that doesn't run on the main thread.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=174036872

library/core/src/androidTest/java/com/google/android/exoplayer2/offline/DownloadManagerTest.java

@@ -28,7 +28,6 @@ import com.google.android.exoplayer2.util.Util;
 import java.io.DataOutputStream;
 import java.io.File;
 import java.io.IOException;
-import java.util.concurrent.Executors;
 import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 
@@ -54,7 +53,7 @@ public class DownloadManagerTest extends InstrumentationTestCase {
     actionFile = Util.createTempFile(getInstrumentation().getContext(), "ExoPlayerTest");
     downloadManager = new DownloadManager(
         new DownloaderConstructorHelper(Mockito.mock(Cache.class), DummyDataSource.FACTORY),
-        Executors.newCachedThreadPool(), actionFile.getAbsolutePath());
+        100, actionFile.getAbsolutePath());
 
     downloadFinishedCondition = new ConditionVariable();
     downloadManager.setListener(new TestDownloadListener());
@@ -120,24 +119,24 @@ public class DownloadManagerTest extends InstrumentationTestCase {
     removeAction1.post().assertDoesNotStart();
 
     // downloadAction2 finishes but it isn't enough to start removeAction1.
-    downloadAction2.finishAndAssertFinished();
+    downloadAction2.finish().assertCancelled();
     removeAction1.assertDoesNotStart();
     // downloadAction3 is post to DownloadManager but it waits for removeAction1 to finish.
     downloadAction3.post().assertDoesNotStart();
 
     // When downloadAction1 finishes, removeAction1 starts.
-    downloadAction1.finishAndAssertFinished();
+    downloadAction1.finish().assertCancelled();
     removeAction1.assertStarted();
     // downloadAction3 still waits removeAction1
     downloadAction3.assertDoesNotStart();
 
     // removeAction2 is posted. removeAction1 and downloadAction3 is canceled so removeAction2
     // starts immediately.
-    removeAction2.post().assertStarted().finishAndAssertFinished();
+    removeAction2.post().assertStarted().finish().assertEnded();
     blockUntilTasksCompleteAndThrowAnyDownloadError();
   }
 
-  public void testMultipleWaitingAction() throws Throwable {
+  public void testMultipleRemoveActionWaitsLastCancelsAllOther() throws Throwable {
     FakeDownloadAction removeAction1 = createRemoveAction("media 1").ignoreInterrupts();
     FakeDownloadAction removeAction2 = createRemoveAction("media 1");
     FakeDownloadAction removeAction3 = createRemoveAction("media 1");
@@ -146,15 +145,70 @@ public class DownloadManagerTest extends InstrumentationTestCase {
     removeAction2.post().assertDoesNotStart();
     removeAction3.post().assertDoesNotStart();
 
-    removeAction1.finishAndAssertFinished();
+    removeAction2.assertCancelled();
-    removeAction2.assertTaskState(DownloadTask.STATE_CANCELLED);
+
-    removeAction3.assertStarted().finishAndAssertFinished();
+    removeAction1.finish().assertCancelled();
+    removeAction3.assertStarted().finish().assertEnded();
+
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  public void testMultipleWaitingDownloadActionStartsInParallel() throws Throwable {
+    FakeDownloadAction removeAction = createRemoveAction("media 1").ignoreInterrupts();
+    FakeDownloadAction downloadAction1 = createDownloadAction("media 1");
+    FakeDownloadAction downloadAction2 = createDownloadAction("media 1");
+
+    removeAction.post().assertStarted();
+    downloadAction1.post().assertDoesNotStart();
+    downloadAction2.post().assertDoesNotStart();
+
+    removeAction.finish().assertEnded();
+    downloadAction1.assertStarted();
+    downloadAction2.assertStarted();
+    downloadAction1.finish().assertEnded();
+    downloadAction2.finish().assertEnded();
+
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  public void testDifferentMediaDownloadActionsPreserveOrder() throws Throwable {
+    FakeDownloadAction removeAction = createRemoveAction("media 1").ignoreInterrupts();
+    FakeDownloadAction downloadAction1 = createDownloadAction("media 1");
+    FakeDownloadAction downloadAction2 = createDownloadAction("media 2");
+
+    removeAction.post().assertStarted();
+    downloadAction1.post().assertDoesNotStart();
+    downloadAction2.post().assertDoesNotStart();
+
+    removeAction.finish().assertEnded();
+    downloadAction1.assertStarted();
+    downloadAction2.assertStarted();
+    downloadAction1.finish().assertEnded();
+    downloadAction2.finish().assertEnded();
+
+    blockUntilTasksCompleteAndThrowAnyDownloadError();
+  }
+
+  public void testDifferentMediaRemoveActionsDoNotPreserveOrder() throws Throwable {
+    FakeDownloadAction downloadAction = createDownloadAction("media 1").ignoreInterrupts();
+    FakeDownloadAction removeAction1 = createRemoveAction("media 1");
+    FakeDownloadAction removeAction2 = createRemoveAction("media 2");
+
+    downloadAction.post().assertStarted();
+    removeAction1.post().assertDoesNotStart();
+    removeAction2.post().assertStarted();
+
+    downloadAction.finish().assertCancelled();
+    removeAction2.finish().assertEnded();
+
+    removeAction1.assertStarted();
+    removeAction1.finish().assertEnded();
 
     blockUntilTasksCompleteAndThrowAnyDownloadError();
   }
 
   private void doTestActionRuns(FakeDownloadAction action) throws Throwable {
-    action.post().assertStarted().finishAndAssertFinished();
+    action.post().assertStarted().finish().assertEnded();
     blockUntilTasksCompleteAndThrowAnyDownloadError();
   }
 
@@ -163,10 +217,10 @@ public class DownloadManagerTest extends InstrumentationTestCase {
     action1.ignoreInterrupts().post().assertStarted();
     action2.post().assertDoesNotStart();
 
-    action1.finishAndAssertFinished();
+    action1.finish();
     action2.assertStarted();
 
-    action2.finishAndAssertFinished();
+    action2.finish().assertEnded();
     blockUntilTasksCompleteAndThrowAnyDownloadError();
   }
 
@@ -174,8 +228,8 @@ public class DownloadManagerTest extends InstrumentationTestCase {
       FakeDownloadAction action2) throws Throwable {
     action1.post().assertStarted();
     action2.post().assertStarted();
-    action1.finishAndAssertFinished();
+    action1.finish().assertEnded();
-    action2.finishAndAssertFinished();
+    action2.finish().assertEnded();
     blockUntilTasksCompleteAndThrowAnyDownloadError();
   }
 
@@ -265,7 +319,7 @@ public class DownloadManagerTest extends InstrumentationTestCase {
       return downloader;
     }
 
-    private FakeDownloadAction post() throws DownloadException {
+    private FakeDownloadAction post() {
       downloadTask = downloadManager.handleAction(this);
       return this;
     }
@@ -277,20 +331,27 @@ public class DownloadManagerTest extends InstrumentationTestCase {
 
     private FakeDownloadAction assertStarted() {
       assertTrue(downloader.started.block(ASSERT_TRUE_TIMEOUT));
-      assertTaskState(DownloadTask.STATE_STARTED);
+      assertState(DownloadTask.STATE_STARTED);
       return this;
     }
 
-    private FakeDownloadAction assertTaskState(@State int state) {
+    private FakeDownloadAction assertEnded() {
+      return assertState(DownloadTask.STATE_ENDED);
+    }
+
+    private FakeDownloadAction assertCancelled() {
+      return assertState(DownloadTask.STATE_CANCELED);
+    }
+
+    private FakeDownloadAction assertState(@State int state) {
       assertTrue(stateChanged.block(ASSERT_TRUE_TIMEOUT));
       stateChanged.close();
       assertEquals(state, downloadTask.getState());
       return this;
     }
 
-    private FakeDownloadAction finishAndAssertFinished() {
+    private FakeDownloadAction finish() {
       downloader.finish.open();
-      assertTaskState(DownloadTask.STATE_ENDED);
       return this;
     }