[Cronet] Change interface APIs to abstract classes

components/cronet/android/test/javatests/src/org/chromium/net/TestDrivenDataProvider.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.net;
 
 import android.os.ConditionVariable;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.List;
 import java.util.concurrent.Executor;
 
 /**
  * An UploadDataProvider that allows tests to invoke {@code onReadSucceeded}
  * and {@code onRewindSucceeded} on the UploadDataSink directly.
  * Chunked mode is not supported here, since the main interest is to test
  * different order of init/read/rewind calls.
  */
-class TestDrivenDataProvider implements UploadDataProvider {
+class TestDrivenDataProvider extends UploadDataProvider {
     private final Executor mExecutor;
     private final List<byte[]> mReads;
     private final ConditionVariable mWaitForReadRequest =
             new ConditionVariable();
     private final ConditionVariable mWaitForRewindRequest =
             new ConditionVariable();
     // Lock used to synchronize access to mReadPending and mRewindPending.
     private final Object mLock = new Object();
 
     private int mNextRead = 0;
@@ skipping 152 matching lines @@
     }
 
     /**
      * Helper method to ensure no read or rewind is in progress.
      */
     private void assertIdle() {
         assertReadNotPending();
         assertRewindNotPending();
     }
 }