Adds method to provide custom AudioManager at runtime.

media/audio/audio_manager_factory_unittest.cc

+// 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.
+
+#include "base/memory/scoped_ptr.h"
+#include "media/audio/audio_manager.h"
+#include "media/audio/audio_manager_factory.h"
+#include "media/audio/fake_audio_log_factory.h"
+#include "media/audio/fake_audio_manager.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+namespace {
+
+class FakeAudioManagerFactory : public AudioManagerFactory {
+ public:
+  FakeAudioManagerFactory() {}
+  ~FakeAudioManagerFactory() override {}
+
+  AudioManager* CreateInstance(AudioLogFactory* audio_log_factory) override {
+    // |created_instance_| is used for verifying. Ownership is transferred to
+    // caller.
+    created_instance_ = new FakeAudioManager(audio_log_factory);
+    return created_instance_;
+  }
+
+  AudioManager* created_instance() { return created_instance_; }
+
+ private:
+  AudioManager* created_instance_;
+};
+
+}  // namespace
+
+// Verifies that SetFactory has the intended effect.
+TEST(AudioManagerFactoryTest, CreateInstance) {
+  // Create an audio manager and verify that it is not null.
+  scoped_ptr<AudioManager> manager(AudioManager::CreateForTesting());
+  ASSERT_NE(nullptr, manager.get());
+  manager.reset();
+
+  // Set the factory. Note that ownership of |factory| is transferred to
+  // AudioManager.
+  FakeAudioManagerFactory* factory = new FakeAudioManagerFactory();
+  AudioManager::SetFactory(factory);
+
+  // Create the AudioManager instance. Verify that it matches the instance
+  // provided by the factory.
+  manager.reset(AudioManager::CreateForTesting());
+  ASSERT_NE(nullptr, manager.get());
+  ASSERT_EQ(factory->created_instance(), manager.get());
+
+  // Reset AudioManagerFactory to prevent factory from persisting to other
+  // tests on the same process. |manager| will reset when scope exits.
+  AudioManager::ResetFactoryForTesting();
+}
+
+}  // namespace media