Replace MockFilterCallback with MockCallback and simplify unit tests.

media/base/mock_callback.cc

+// Copyright (c) 2011 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.
+
+#include "media/base/mock_callback.h"
+
+using ::testing::_;
+using ::testing::StrictMock;
+
+namespace media {
+
+MockCallback::MockCallback() {}
+
+MockCallback::~MockCallback() {
+  Destructor();
+}
+
+MockCallback* NewExpectedCallback() {
+  StrictMock<MockCallback>* callback = new StrictMock<MockCallback>();
+  EXPECT_CALL(*callback, RunWithParams(_));
+  EXPECT_CALL(*callback, Destructor());
+  return callback;
+}
+
+}  // namespace media