Break out WebAudio suspension code into new class. Add tests.

media/base/silent_sink_suspender_unittest.cc

Index: media/base/silent_sink_suspender_unittest.cc
diff --git a/media/base/silent_sink_suspender_unittest.cc b/media/base/silent_sink_suspender_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c69084b4c32593bffdb0cc9e86ed72e8cdd8da86
--- /dev/null
+++ b/media/base/silent_sink_suspender_unittest.cc
@@ -0,0 +1,160 @@
+// Copyright 2016 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/run_loop.h"
+#include "base/test/test_message_loop.h"
+#include "media/base/fake_audio_render_callback.h"
+#include "media/base/mock_audio_renderer_sink.h"
+#include "media/base/silent_sink_suspender.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+ACTION_P(RunClosure, closure) {
+  closure.Run();
+}
+
+class SilentSinkSuspenderTest : public testing::Test {
+ public:
+  SilentSinkSuspenderTest()
+      : params_(AudioParameters::AUDIO_FAKE,
+                CHANNEL_LAYOUT_MONO,
+                44100,
+                8,
+                128),
+        mock_sink_(new testing::StrictMock<MockAudioRendererSink>()),
+        fake_callback_(0.1),
+        temp_bus_(AudioBus::Create(params_)),
+        // Set a negative timeout so any silence will suspend immediately.
+        suspender_(&fake_callback_,
+                   base::TimeDelta::FromSeconds(-1),
+                   params_,
+                   mock_sink_,
+                   test_loop_.task_runner()) {}
+  ~SilentSinkSuspenderTest() override {}
+
+ protected:
+  base::TestMessageLoop test_loop_;
+  const AudioParameters params_;
+  scoped_refptr<testing::StrictMock<MockAudioRendererSink>> mock_sink_;
+  FakeAudioRenderCallback fake_callback_;
+  std::unique_ptr<AudioBus> temp_bus_;
+  SilentSinkSuspender suspender_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SilentSinkSuspenderTest);
+};
+
+TEST_F(SilentSinkSuspenderTest, BasicPassthough) {
+  temp_bus_->Zero();
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_FALSE(temp_bus_->AreFramesZero());
+}
+
+TEST_F(SilentSinkSuspenderTest, SuspendResumeTriggered) {
+  // Verify a normal Render() doesn't invoke suspend.
+  EXPECT_FALSE(suspender_.is_using_fake_sink_for_testing());
+  temp_bus_->Zero();
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_FALSE(temp_bus_->AreFramesZero());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(suspender_.is_using_fake_sink_for_testing());
+
+  // Mute all audio generated by the callback, this should suspend immediately.
+  fake_callback_.set_volume(0);
+  temp_bus_->Zero();
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_TRUE(temp_bus_->AreFramesZero());
+  {
+    base::RunLoop run_loop;
+    EXPECT_CALL(*mock_sink_, Pause())
+        .WillOnce(RunClosure(run_loop.QuitClosure()));
+    run_loop.Run();
+    EXPECT_TRUE(suspender_.is_using_fake_sink_for_testing());
+  }
+
+  // Unmute the audio, the FakeWorker inside |suspender_| should be running now,
+  // so we don't need to manually invoke Render().
+  fake_callback_.reset();
+  fake_callback_.set_volume(1);
+  {
+    base::RunLoop run_loop;
+    EXPECT_CALL(*mock_sink_, Play())
+        .WillOnce(RunClosure(run_loop.QuitClosure()));
+    run_loop.Run();
+    EXPECT_FALSE(suspender_.is_using_fake_sink_for_testing());
+  }
+
+  // The first Render() after resume should return the first buffer which was
+  // not silent.
+  fake_callback_.reset();
+  std::unique_ptr<AudioBus> true_bus = AudioBus::Create(params_);
+  fake_callback_.Render(true_bus.get(), 0, 0);
+  EXPECT_FALSE(true_bus->AreFramesZero());
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_EQ(memcmp(temp_bus_->channel(0), true_bus->channel(0),
+                   temp_bus_->frames() * sizeof(float)),
+            0);
+}
+
+TEST_F(SilentSinkSuspenderTest, MultipleSuspend) {
+  // Mute all audio generated by the callback, this should suspend immediately.
+  fake_callback_.set_volume(0);
+  temp_bus_->Zero();
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_TRUE(temp_bus_->AreFramesZero());
+
+  // A second render should only result in a single Pause() call.
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+
+  EXPECT_CALL(*mock_sink_, Pause());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(suspender_.is_using_fake_sink_for_testing());
+}
+
+TEST_F(SilentSinkSuspenderTest, MultipleResume) {
+  // Mute all audio generated by the callback, this should suspend immediately.
+  fake_callback_.set_volume(0);
+  temp_bus_->Zero();
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_TRUE(temp_bus_->AreFramesZero());
+  EXPECT_CALL(*mock_sink_, Pause());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(suspender_.is_using_fake_sink_for_testing());
+
+  // Unmute the data.
+  fake_callback_.set_volume(1);
+
+  // Prepare our equality testers.
+  fake_callback_.reset();
+  std::unique_ptr<AudioBus> true_bus1 = AudioBus::Create(params_);
+  fake_callback_.Render(true_bus1.get(), 0, 0);
+  std::unique_ptr<AudioBus> true_bus2 = AudioBus::Create(params_);
+  fake_callback_.Render(true_bus2.get(), 0, 0);
+  EXPECT_NE(memcmp(true_bus1->channel(0), true_bus2->channel(0),
+                   true_bus1->frames() * sizeof(float)),
+            0);
+
+  // Reset the fake callback data generation and force two Render() calls before
+  // the sink can transition.
+  fake_callback_.reset();
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(nullptr, 0, 0));
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(nullptr, 0, 0));
+  EXPECT_CALL(*mock_sink_, Play());
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(suspender_.is_using_fake_sink_for_testing());
+
+  // Each render after resuming should return one of the non-silent bus.
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_EQ(memcmp(temp_bus_->channel(0), true_bus1->channel(0),
+                   temp_bus_->frames() * sizeof(float)),
+            0);
+  EXPECT_EQ(temp_bus_->frames(), suspender_.Render(temp_bus_.get(), 0, 0));
+  EXPECT_EQ(memcmp(temp_bus_->channel(0), true_bus2->channel(0),
+                   temp_bus_->frames() * sizeof(float)),
+            0);
+}
+
+}  // namespace content