Allow MediaSession in iframes to be routed

content/browser/media/session/media_session_impl.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 "content/browser/media/session/media_session_impl.h"
 
 #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"
 #include "content/public/browser/media_session.h"
 #include "content/public/browser/media_session_observer.h"
 #include "content/public/browser/web_contents.h"
 #include "media/base/media_content_type.h"
 
 #if defined(OS_ANDROID)
 #include "content/browser/media/session/media_session_android.h"
 #endif  // defined(OS_ANDROID)
 
 namespace content {
 
 namespace {
 
 const double kDefaultVolumeMultiplier = 1.0;
 const double kDuckingVolumeMultiplier = 0.2;
 
+size_t ComputeFrameDepth(RenderFrameHost* rfh) {
+  size_t depth = 0;
+  while (rfh) {
+    ++depth;
+    rfh = rfh->GetParent();

[whywhat, 2016/12/01 22:13:00]

nit: this could still result in an N-square complexity if you have N frames
nested into each other, right?
maybe RenderFrameHost could get a GetDepth() method that caches the result...

[Zhiqiang Zhang (Slow), 2016/12/02 14:17:28]

Now using a cache to compute the depths, so the complexity is O(N).
Better not to do in this CL, since we are the only user.

+  }
+  return depth;
+}
+
 }  // anonymous namespace
 
 using MediaSessionSuspendedSource =
     MediaSessionUmaHelper::MediaSessionSuspendedSource;
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(MediaSessionImpl);
 
 MediaSessionImpl::PlayerIdentifier::PlayerIdentifier(
     MediaSessionPlayerObserver* observer,
     int player_id)
@@ skipping 44 matching lines @@
   // TODO(zqzhang): refactor MediaSessionImpl, maybe move the interface used to
   // talk with AudioFocusManager out to a seperate class. The AudioFocusManager
   // unit tests then could mock the interface and abandon audio focus when
   // WebContents is destroyed. See https://crbug.com/651069
   normal_players_.clear();
   pepper_players_.clear();
   one_shot_players_.clear();
   AbandonSystemAudioFocusIfNeeded();
 }
 
-void MediaSessionImpl::SetMediaSessionService(
-    MediaSessionServiceImpl* service) {
-  service_ = service;
-}
-
 void MediaSessionImpl::AddObserver(MediaSessionObserver* observer) {
   observers_.AddObserver(observer);
 }
 
 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) {
   if (media_content_type == media::MediaContentType::OneShot)
     return AddOneShotPlayer(observer, player_id);
   if (media_content_type == media::MediaContentType::Pepper)
     return AddPepperPlayer(observer, player_id);
 
   observer->OnSetVolumeMultiplier(player_id, GetVolumeMultiplier());
 
@@ skipping 21 matching lines @@
 
   if (audio_focus_state_ != State::ACTIVE)
     return false;
 
   // The session should be reset if a player is starting while all players are
   // suspended.
   if (old_audio_focus_state != State::ACTIVE)
     normal_players_.clear();
 
   normal_players_.insert(PlayerIdentifier(observer, player_id));
+
+  UpdateRoutedService();
   NotifyAboutStateChange();
-
   return true;
 }
 
 void MediaSessionImpl::RemovePlayer(MediaSessionPlayerObserver* observer,
                                     int player_id) {
   bool was_controllable = IsControllable();
 
   PlayerIdentifier identifier(observer, player_id);
 
   auto it = normal_players_.find(identifier);
   if (it != normal_players_.end())
     normal_players_.erase(it);
 
   it = pepper_players_.find(identifier);
   if (it != pepper_players_.end())
     pepper_players_.erase(it);
 
   it = one_shot_players_.find(identifier);
   if (it != one_shot_players_.end())
     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
   // about the state change.
   if (!was_controllable && IsControllable())
     NotifyAboutStateChange();
 }
 
 void MediaSessionImpl::RemovePlayers(MediaSessionPlayerObserver* observer) {
   bool was_controllable = IsControllable();
@@ skipping 13 matching lines @@
   }
 
   for (auto it = one_shot_players_.begin(); it != one_shot_players_.end();) {
     if (it->observer == observer)
       one_shot_players_.erase(it++);
     else
       ++it;
   }
 
   AbandonSystemAudioFocusIfNeeded();
+  UpdateRoutedService();
 
   // The session may become controllable after removing a one-shot player.
   // However AbandonSystemAudioFocusIfNeeded will short-return and won't notify
   // about the state change.
   if (!was_controllable && IsControllable())
     NotifyAboutStateChange();
 }
 
 void MediaSessionImpl::RecordSessionDuck() {
   uma_helper_.RecordSessionSuspended(
@@ skipping 72 matching lines @@
 
   if (audio_focus_state_ != State::SUSPENDED)
     OnSuspendInternal(suspend_type, State::SUSPENDED);
 
   DCHECK(audio_focus_state_ == State::SUSPENDED);
   normal_players_.clear();
 
   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;
   is_ducking_ = true;
   UpdateVolumeMultiplier();
 }
 
 void MediaSessionImpl::StopDucking() {
   if (!is_ducking_)
     return;
@@ skipping 133 matching lines @@
 
   NotifyAboutStateChange();
 }
 
 MediaSessionImpl::MediaSessionImpl(WebContents* web_contents)
     : WebContentsObserver(web_contents),
       audio_focus_state_(State::INACTIVE),
       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)
 }
 
 void MediaSessionImpl::Initialize() {
   delegate_ = AudioFocusDelegate::Create(this);
 }
 
 bool MediaSessionImpl::RequestSystemAudioFocus(
@@ skipping 61 matching lines @@
                                         int player_id) {
   if (!RequestSystemAudioFocus(AudioFocusManager::AudioFocusType::Gain))
     return false;
 
   one_shot_players_.insert(PlayerIdentifier(observer, player_id));
   NotifyAboutStateChange();
 
   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() {
+  MediaSessionServiceImpl* new_service = ComputeServiceForRouting();
+  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>());
+  }
+}
+
+MediaSessionServiceImpl* MediaSessionImpl::ComputeServiceForRouting() {
+  // The service selection strategy is: Select a frame that has a playing/paused

[whywhat, 2016/12/01 22:13:00]

nit: s/Select/select/

[Zhiqiang Zhang (Slow), 2016/12/02 14:17:28]

Done.

+  // player and has a corresponding MediaSessionService and return the
+  // corresponding MediaSessionService. If multiple frames satisfy the criteria,
+  // prefer the top-most frame.
+  std::set<RenderFrameHost*> frames;
+  for (const auto& player : normal_players_) {
+    RenderFrameHost* frame = player.observer->GetRenderFrameHost();
+    if (frame)
+      frames.insert(frame);
+  }
+
+  for (const auto& player : one_shot_players_) {
+    RenderFrameHost* frame = player.observer->GetRenderFrameHost();
+    if (frame)
+      frames.insert(frame);
+  }
+
+  for (const auto& player : pepper_players_) {

[whywhat, 2016/12/01 22:13:00]

does it make sense to check these if they will never return a non-null render
frame host?
same above for one_shot_players I assume?

[Zhiqiang Zhang (Slow), 2016/12/02 14:17:28]

This is https://crbug.com/670273. Pepper players should have associated RFH, but
currently there's a mistake.

+    RenderFrameHost* frame = player.observer->GetRenderFrameHost();
+    if (frame)
+      frames.insert(frame);
+  }
+
+  RenderFrameHost* best_frame = nullptr;
+  size_t min_depth = std::numeric_limits<size_t>::max();
+
+  for (RenderFrameHost* frame : frames) {
+    size_t depth = ComputeFrameDepth(frame);
+    if (depth >= min_depth)
+      continue;
+    if (!IsServiceActiveForRenderFrameHost(frame))
+      continue;
+    best_frame = frame;
+    min_depth = depth;
+  }
+
+  return best_frame ? services_[best_frame] : nullptr;
+}
+
 }  // namespace content