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..bdd2011b89e90a2a479f49ffedb2786e6e6d3e3f 100644
--- a/content/browser/media/session/media_session_impl.cc
+++ b/content/browser/media/session/media_session_impl.cc
@@ -6,6 +6,7 @@
 
 #include <algorithm>
 #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"
 #include "content/browser/media/session/media_session_service_impl.h"
 #include "content/browser/web_contents/web_contents_impl.h"
@@ -89,11 +90,6 @@ void MediaSessionImpl::WebContentsDestroyed() {
   AbandonSystemAudioFocusIfNeeded();
 }
 
-void MediaSessionImpl::SetMediaSessionService(
-    MediaSessionServiceImpl* service) {
-  service_ = service;
-}
-
 void MediaSessionImpl::AddObserver(MediaSessionObserver* observer) {
   observers_.AddObserver(observer);
 }
@@ -102,13 +98,18 @@ 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 +151,9 @@ bool MediaSessionImpl::AddPlayer(MediaSessionPlayerObserver* observer,
     normal_players_.clear();
 
   normal_players_.insert(PlayerIdentifier(observer, player_id));
-  NotifyAboutStateChange();
 
+  UpdateRoutedService();
+  NotifyAboutStateChange();
   return true;
 }
 
@@ -174,6 +176,7 @@ void MediaSessionImpl::RemovePlayer(MediaSessionPlayerObserver* observer,
     one_shot_players_.erase(it);
 
   AbandonSystemAudioFocusIfNeeded();
+  UpdateRoutedService();
 
   // The session may become controllable after removing a one-shot player.
   // However AbandonSystemAudioFocusIfNeeded will short-return and won't notify
@@ -207,6 +210,7 @@ void MediaSessionImpl::RemovePlayers(MediaSessionPlayerObserver* observer) {
   }
 
   AbandonSystemAudioFocusIfNeeded();
+  UpdateRoutedService();
 
   // The session may become controllable after removing a one-shot player.
   // However AbandonSystemAudioFocusIfNeeded will short-return and won't notify
@@ -299,24 +303,6 @@ void MediaSessionImpl::Stop(SuspendType suspend_type) {
   AbandonSystemAudioFocusIfNeeded();
 }
 
-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);
-}
-
-void MediaSessionImpl::OnMediaSessionDisabledAction(
-    blink::mojom::MediaSessionAction action) {
-  for (auto& observer : observers_)
-    observer.MediaSessionDisabledAction(action);
-}
-
 void MediaSessionImpl::StartDucking() {
   if (is_ducking_)
     return;
@@ -470,7 +456,7 @@ MediaSessionImpl::MediaSessionImpl(WebContents* web_contents)
       audio_focus_type_(
           AudioFocusManager::AudioFocusType::GainTransientMayDuck),
       is_ducking_(false),
-      service_(nullptr) {
+      routed_service_(nullptr) {
 #if defined(OS_ANDROID)
   session_android_.reset(new MediaSessionAndroid(this));
 #endif  // defined(OS_ANDROID)
@@ -552,4 +538,97 @@ bool MediaSessionImpl::AddOneShotPlayer(MediaSessionPlayerObserver* observer,
   return true;
 }
 
+// MediaSessionService-related methods
+
+void MediaSessionImpl::OnServiceCreated(
+    MediaSessionServiceImpl* service) {
+  services_[service->GetRenderFrameHost()] = service;
+}
+
+void MediaSessionImpl::OnServiceDestroyed(
+    MediaSessionServiceImpl* service) {
+  services_.erase(service->GetRenderFrameHost());
+}
+
+void MediaSessionImpl::OnMediaSessionMetadataChanged(
+    MediaSessionServiceImpl* service) {
+  if (service != routed_service_)
+    return;
+
+  NotifyMediaSessionMetadataChange(routed_service_->metadata());
+}
+
+void MediaSessionImpl::OnMediaSessionActionsChanged(
+    MediaSessionServiceImpl* service) {
+  if (service != routed_service_)
+    return;
+
+  NotifyMediaSessionActionsChange(routed_service_->actions());
+}
+
+void MediaSessionImpl::DidReceiveAction(
+    blink::mojom::MediaSessionAction action) {
+  if (!routed_service_)
+    return;
+
+  routed_service_->GetClient()->DidReceiveAction(action);
+}
+
+bool MediaSessionImpl::IsServiceActiveForRenderFrameHost(
+    RenderFrameHost* rfh) {
+  if (!services_.count(rfh))
+    return false;
+
+  return services_[rfh]->metadata().has_value() ||
+         !services_[rfh]->actions().empty();
+}
+
+void MediaSessionImpl::UpdateRoutedService() {
+  RenderFrameHost* rfh = GetMostMeaningfulAudioProducingFrame();
+  MediaSessionServiceImpl* new_service = nullptr;
+  if (services_.count(rfh))
+    new_service = services_[rfh];
+
+  if (new_service == routed_service_)
+    return;
+
+  routed_service_ = new_service;
+  if (routed_service_) {
+    NotifyMediaSessionMetadataChange(routed_service_->metadata());
+    NotifyMediaSessionActionsChange(routed_service_->actions());
+  } else {
+    NotifyMediaSessionMetadataChange(base::nullopt);
+    NotifyMediaSessionActionsChange(
+        std::set<blink::mojom::MediaSessionAction>());
+  }
+}
+
+RenderFrameHost* MediaSessionImpl::GetMostMeaningfulAudioProducingFrame() {
+  // TODO(zqzhang): improve the selection of most-meaningful player. See
+  // https://crbug.com/xxxxxx
+
+  // Prefer top-level session.
+  RenderFrameHost* main_frame = web_contents()->GetMainFrame();

[Zhiqiang Zhang (Slow), 2016/11/25 14:50:41]

This was the current plan when I talked with Mounir.

After implementing this, I'm a bit worried about security here. This means the
top-level frame can listen to whether the embedded iframe plays audio. WDYT?

+  if (IsServiceActiveForRenderFrameHost(main_frame)) {
+    return main_frame;
+  }
+
+  // If not, select an audio-producing frame arbitrarily.
+  MediaSessionPlayerObserver* player_observer = nullptr;
+  if (!normal_players_.empty())
+    player_observer = normal_players_.begin()->observer;
+  else if (!one_shot_players_.empty())
+    player_observer = one_shot_players_.begin()->observer;
+  else if (!pepper_players_.empty())
+    player_observer = pepper_players_.begin()->observer;
+
+  MediaSessionController* controller = static_cast<MediaSessionController*>(
+      player_observer);
+
+  if (!controller)
+    return nullptr;
+
+  return controller->id().first;
+}
+
 }  // namespace content