Allow MediaSession in iframes to be routed

content/browser/media/session/media_session_impl.cc

Index: content/browser/media/session/media_session_impl.cc
diff --git a/content/browser/media/session/media_session_impl.cc b/content/browser/media/session/media_session_impl.cc
index 1b5e706c47a32b0167e2306d9c7b7dc3cd5b1a41..da00fe3e82645ccb08d659a17907361c540813cc 100644
--- a/content/browser/media/session/media_session_impl.cc
+++ b/content/browser/media/session/media_session_impl.cc
@@ -8,6 +8,7 @@
 #include "content/browser/media/session/audio_focus_delegate.h"
 #include "content/browser/media/session/media_session_player_observer.h"
 #include "content/browser/media/session/media_session_service_impl.h"
+#include "content/browser/media/session/media_session_service_router.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/media_session.h"
 #include "content/public/browser/media_session_observer.h"
@@ -89,9 +90,19 @@ void MediaSessionImpl::WebContentsDestroyed() {
   AbandonSystemAudioFocusIfNeeded();
 }
 
-void MediaSessionImpl::SetMediaSessionService(
-    MediaSessionServiceImpl* service) {
-  service_ = service;
+MediaSessionPlayerObserver*
+MediaSessionImpl::GetMostMeaningfulPlayerObserver() {
+  MediaSessionPlayerObserver* player_observer = nullptr;
+  // TODO(zqzhang): improve the selection of most-meaningful player. See
+  // https://crbug.com/xxxxxx
+  if (!normal_players_.empty())
+    return player_observer = normal_players_.begin()->observer;
+  if (!one_shot_players_.empty())
+    return player_observer = one_shot_players_.begin()->observer;
+  if (!pepper_players_.empty())
+    return player_observer = pepper_players_.begin()->observer;
+
+  return nullptr;
 }
 
 void MediaSessionImpl::AddObserver(MediaSessionObserver* observer) {
@@ -102,13 +113,18 @@ void MediaSessionImpl::RemoveObserver(MediaSessionObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
-void MediaSessionImpl::SetMetadata(
+void MediaSessionImpl::NotifyMediaSessionMetadataChange(
     const base::Optional<MediaMetadata>& metadata) {
-  metadata_ = metadata;
   for (auto& observer : observers_)
     observer.MediaSessionMetadataChanged(metadata);
 }
 
+void MediaSessionImpl::NotifyMediaSessionActionsChange(
+    const std::set<blink::mojom::MediaSessionAction>& actions) {
+  for (auto& observer : observers_)
+    observer.MediaSessionActionsChanged(actions);
+}
+
 bool MediaSessionImpl::AddPlayer(MediaSessionPlayerObserver* observer,
                                  int player_id,
                                  media::MediaContentType media_content_type) {
@@ -150,8 +166,9 @@ bool MediaSessionImpl::AddPlayer(MediaSessionPlayerObserver* observer,
     normal_players_.clear();
 
   normal_players_.insert(PlayerIdentifier(observer, player_id));
-  NotifyAboutStateChange();
 
+  service_router_->MostMeaningfulPlayerObserverMayHaveChanged();
+  NotifyAboutStateChange();
   return true;
 }
 
@@ -174,6 +191,7 @@ void MediaSessionImpl::RemovePlayer(MediaSessionPlayerObserver* observer,
     one_shot_players_.erase(it);
 
   AbandonSystemAudioFocusIfNeeded();
+  service_router_->MostMeaningfulPlayerObserverMayHaveChanged();
 
   // The session may become controllable after removing a one-shot player.
   // However AbandonSystemAudioFocusIfNeeded will short-return and won't notify
@@ -207,6 +225,7 @@ void MediaSessionImpl::RemovePlayers(MediaSessionPlayerObserver* observer) {
   }
 
   AbandonSystemAudioFocusIfNeeded();
+  service_router_->MostMeaningfulPlayerObserverMayHaveChanged();
 
   // The session may become controllable after removing a one-shot player.
   // However AbandonSystemAudioFocusIfNeeded will short-return and won't notify
@@ -301,20 +320,13 @@ void MediaSessionImpl::Stop(SuspendType suspend_type) {
 
 void MediaSessionImpl::DidReceiveAction(
     blink::mojom::MediaSessionAction action) {
-  if (service_)
-    service_->GetClient()->DidReceiveAction(action);
-}
-
-void MediaSessionImpl::OnMediaSessionEnabledAction(
-    blink::mojom::MediaSessionAction action) {
-  for (auto& observer : observers_)
-    observer.MediaSessionEnabledAction(action);
+  GetMediaSessionServiceRouter()->DidReceiveAction(action);
 }
 
-void MediaSessionImpl::OnMediaSessionDisabledAction(
-    blink::mojom::MediaSessionAction action) {
+void MediaSessionImpl::OnMediaSessionActionsChanged(
+    const std::set<blink::mojom::MediaSessionAction>& action) {
   for (auto& observer : observers_)
-    observer.MediaSessionDisabledAction(action);
+    observer.MediaSessionActionsChanged(action);
 }
 
 void MediaSessionImpl::StartDucking() {
@@ -470,7 +482,7 @@ MediaSessionImpl::MediaSessionImpl(WebContents* web_contents)
       audio_focus_type_(
           AudioFocusManager::AudioFocusType::GainTransientMayDuck),
       is_ducking_(false),
-      service_(nullptr) {
+      service_router_(new MediaSessionServiceRouter(this)) {
 #if defined(OS_ANDROID)
   session_android_.reset(new MediaSessionAndroid(this));
 #endif  // defined(OS_ANDROID)