Add function to set the MediaSession ducking multiplier

This allows an app (Chromecast, e.g.) to change the multiplier and better
control ducking behavior.

Bug: internal b/69630398
Test: Ran on Android Things speaker with different multipliers,
      observed proper ducking volume.

Change-Id: I5078fd11606a5d648aca9b17938c3c8caefd3826
Reviewed-on: https://chromium-review.googlesource.com/942055Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Stephen Lanham <slan@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Chris Kuiper <ckuiper@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541209}

chromecast/browser/cast_media_blocker_unittest.cc

@@ -36,6 +36,7 @@ class MockMediaSession : public content::MediaSession {
   MOCK_CONST_METHOD0(IsActuallyPaused, bool());
   MOCK_METHOD0(StartDucking, void());
   MOCK_METHOD0(StopDucking, void());
+  MOCK_METHOD1(SetDuckingVolumeMultiplier, void(double));
   MOCK_METHOD1(DidReceiveAction, void(blink::mojom::MediaSessionAction));
   MOCK_METHOD1(AddObserver, void(content::MediaSessionObserver*));
   MOCK_METHOD1(RemoveObserver, void(content::MediaSessionObserver*));

content/browser/media/session/media_session_impl.cc

@@ -7,6 +7,7 @@
 #include <algorithm>
 
 #include "base/memory/ptr_util.h"
+#include "base/numerics/ranges.h"
 #include "content/browser/media/session/audio_focus_delegate.h"
 #include "content/browser/media/session/media_session_controller.h"
 #include "content/browser/media/session/media_session_player_observer.h"
@@ -29,8 +30,8 @@ using MediaSessionUserAction = MediaSessionUmaHelper::MediaSessionUserAction;
 
 namespace {
 
-const double kDefaultVolumeMultiplier = 1.0;
-const double kDuckingVolumeMultiplier = 0.2;
+const double kUnduckedVolumeMultiplier = 1.0;
+const double kDefaultDuckingVolumeMultiplier = 0.2;
 
 using MapRenderFrameHostToDepth = std::map<RenderFrameHost*, size_t>;
 
@@ -423,6 +424,10 @@ bool MediaSessionImpl::IsActuallyPaused() const {
   return !IsActive();
 }
 
+void MediaSessionImpl::SetDuckingVolumeMultiplier(double multiplier) {
+  ducking_volume_multiplier_ = base::ClampToRange(multiplier, 0.0, 1.0);
+}
+
 void MediaSessionImpl::StartDucking() {
   if (is_ducking_)
     return;
@@ -445,7 +450,7 @@ void MediaSessionImpl::UpdateVolumeMultiplier() {
 }
 
 double MediaSessionImpl::GetVolumeMultiplier() const {
-  return is_ducking_ ? kDuckingVolumeMultiplier : kDefaultVolumeMultiplier;
+  return is_ducking_ ? ducking_volume_multiplier_ : kUnduckedVolumeMultiplier;
 }
 
 bool MediaSessionImpl::IsActive() const {
@@ -532,7 +537,8 @@ void MediaSessionImpl::OnSuspendInternal(SuspendType suspend_type,
   }
 
   for (const auto& it : pepper_players_)
-    it.observer->OnSetVolumeMultiplier(it.player_id, kDuckingVolumeMultiplier);
+    it.observer->OnSetVolumeMultiplier(it.player_id,
+                                       ducking_volume_multiplier_);
 
   NotifyAboutStateChange();
 }
@@ -558,6 +564,7 @@ MediaSessionImpl::MediaSessionImpl(WebContents* web_contents)
       audio_focus_type_(
           AudioFocusManager::AudioFocusType::GainTransientMayDuck),
       is_ducking_(false),
+      ducking_volume_multiplier_(kDefaultDuckingVolumeMultiplier),
       routed_service_(nullptr) {
 #if defined(OS_ANDROID)
   session_android_.reset(new MediaSessionAndroid(this));
@@ -713,7 +720,7 @@ void MediaSessionImpl::DidReceiveAction(
     for (const auto& player : pepper_players_) {
       if (player.observer->render_frame_host() != rfh_of_routed_service) {
         player.observer->OnSetVolumeMultiplier(player.player_id,
-                                               kDuckingVolumeMultiplier);
+                                               ducking_volume_multiplier_);
       }
     }
     for (const auto& player : one_shot_players_) {

content/browser/media/session/media_session_impl.h

@@ -141,6 +141,9 @@ class MediaSessionImpl : public MediaSession,
   // MediaSessionService declared state and guessed state (audio_focus_state_).
   CONTENT_EXPORT bool IsActuallyPaused() const override;
 
+  // Set the volume multiplier applied during ducking.
+  CONTENT_EXPORT void SetDuckingVolumeMultiplier(double multiplier) override;
+
   // Let the media session start ducking such that the volume multiplier is
   // reduced.
   CONTENT_EXPORT void StartDucking() override;
@@ -302,6 +305,8 @@ class MediaSessionImpl : public MediaSession,
   // StopDucking().
   bool is_ducking_;
 
+  double ducking_volume_multiplier_;
+
   base::CallbackList<void(State)> media_session_state_listeners_;
 
   base::ObserverList<MediaSessionObserver> observers_;

content/browser/media/session/media_session_impl_browsertest.cc

@@ -44,6 +44,7 @@ namespace {
 
 const double kDefaultVolumeMultiplier = 1.0;
 const double kDuckingVolumeMultiplier = 0.2;
+const double kDifferentDuckingVolumeMultiplier = 0.018;
 
 class MockAudioFocusDelegate : public AudioFocusDelegate {
  public:
@@ -314,6 +315,23 @@ IN_PROC_BROWSER_TEST_F(MediaSessionImplBrowserTest,
   EXPECT_EQ(kDefaultVolumeMultiplier, player_observer->GetVolumeMultiplier(2));
 }
 
+IN_PROC_BROWSER_TEST_F(MediaSessionImplBrowserTest,
+                       DuckingUsesConfiguredMultiplier) {
+  auto player_observer = std::make_unique<MockMediaSessionPlayerObserver>();
+
+  StartNewPlayer(player_observer.get(), media::MediaContentType::Persistent);
+  StartNewPlayer(player_observer.get(), media::MediaContentType::Persistent);
+  media_session_->SetDuckingVolumeMultiplier(kDifferentDuckingVolumeMultiplier);
+  SystemStartDucking();
+  EXPECT_EQ(kDifferentDuckingVolumeMultiplier,
+            player_observer->GetVolumeMultiplier(0));
+  EXPECT_EQ(kDifferentDuckingVolumeMultiplier,
+            player_observer->GetVolumeMultiplier(1));
+  SystemStopDucking();
+  EXPECT_EQ(kDefaultVolumeMultiplier, player_observer->GetVolumeMultiplier(0));
+  EXPECT_EQ(kDefaultVolumeMultiplier, player_observer->GetVolumeMultiplier(1));
+}
+
 IN_PROC_BROWSER_TEST_F(MediaSessionImplBrowserTest, AudioFocusInitialState) {
   EXPECT_FALSE(IsActive());
 }

content/public/browser/media_session.h

@@ -70,6 +70,9 @@ class MediaSession {
   // Tell the media session a user action has performed.
   virtual void DidReceiveAction(blink::mojom::MediaSessionAction action) = 0;
 
+  // Set the volume multiplier applied during ducking.
+  virtual void SetDuckingVolumeMultiplier(double multiplier) = 0;
+
   // Let the media session start ducking such that the volume multiplier is
   // reduced.
   virtual void StartDucking() = 0;