Move audio focus control from media/ to content/ and make it per WebContents.

content/browser/media/android/media_session.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/android/media_session.h"
+
+#include "base/android/jni_android.h"
+#include "content/browser/media/android/browser_media_player_manager.h"

[whywhat, 2015/05/12 12:50:45]

You don't need this include.

[mlamouri (slow - plz ping), 2015/05/19 21:56:15]

Done.

+#include "jni/MediaSession_jni.h"
+
+namespace content {
+
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(MediaSession);
+
+// static
+bool content::MediaSession::RegisterMediaSession(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+// static
+MediaSession* MediaSession::Get(WebContents* web_contents) {
+  MediaSession* session = FromWebContents(web_contents);
+  if (!session) {
+    CreateForWebContents(web_contents);
+    session = FromWebContents(web_contents);
+    session->Initialize();
+  }
+  return session;
+}
+
+MediaSession::~MediaSession() {
+  DCHECK(players_.IsEmpty());
+  DCHECK(!has_audio_focus_);
+}
+
+void MediaSession::Initialize() {
+  JNIEnv* env = base::android::AttachCurrentThread();
+  DCHECK(env);
+  j_media_session_.Reset(Java_MediaSession_createMediaSession(
+      env,
+      base::android::GetApplicationContext(),
+      reinterpret_cast<intptr_t>(this)));
+}
+
+MediaSession::MediaSession(WebContents* web_contents)
+    : WebContentsObserver(web_contents)

[whywhat, 2015/05/12 12:50:45]

follow the style guide here that's different from Blink's one:
https://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Constructor_...

[mlamouri (slow - plz ping), 2015/05/19 21:56:15]

Sorry.

+    , has_audio_focus_(false)
+    , audio_focus_type_(Type::Transient) {
+}
+
+bool MediaSession::RequestAudioFocus(MediaSessionDelegate* delegate,
+                                     int player_id,
+                                     Type type) {
+  // If the audio focus is already granted and is of type Content, there is
+  // nothing to do. If it is granted of type Transient the requested type is
+  // also transient, there is also nothing to do. Otherwise, the session needs
+  // to request audio focus again.
+  if (has_audio_focus_ &&

[whywhat, 2015/05/12 12:50:45]

if you had None in Type as the first member, could be simply if (type <=
audio_focus_type_)
not sure if all audio focus types would be sorted by strength.

[mlamouri (slow - plz ping), 2015/05/19 21:56:15]

I wouldn't recommend doing that. I could write a helper method like
IsCurrentAudioFocusSufficient() if you think it would be better.

+      (audio_focus_type_ == Type::Content || audio_focus_type_ == type)) {
+    return true;
+  }
+
+  // The session should be reset if a player is starting while all players are
+  // suspended.
+  if (!has_audio_focus_)
+    players_.Clear();
+
+  players_.Add(new PlayerIdentifier(delegate, player_id));
+
+  JNIEnv* env = base::android::AttachCurrentThread();
+  DCHECK(env);
+  has_audio_focus_ = Java_MediaSession_requestAudioFocus(
+      env, j_media_session_.obj(), type == Type::Transient);
+  audio_focus_type_ = type;
+  return has_audio_focus_;
+}
+
+void MediaSession::AbandonAudioFocus(MediaSessionDelegate* delegate,
+                                     int player_id) {
+  for (PlayersMap::Iterator<PlayerIdentifier> iter(&players_); !iter.IsAtEnd();

[whywhat, 2015/05/12 12:50:45]

why using IDMap if you're not using its ids?
something like hash_map<Delegate*, hash_set<int>> sounds like a better choice
from the first glance.

[mlamouri (slow - plz ping), 2015/05/19 21:56:15]

Done. I'm using a hash_set now. It avoids adding duplicates too.

+       iter.Advance()) {
+    PlayerIdentifier* player_identifier = iter.GetCurrentValue();
+    if (delegate == player_identifier->delegate_ &&
+        player_id == player_identifier->id_) {
+      players_.Remove(iter.GetCurrentKey());
+    }
+  }
+
+  AbandonAudioFocusIfNeeded();
+}
+
+void MediaSession::AbandonAudioFocus(MediaSessionDelegate* delegate) {
+  for (PlayersMap::Iterator<PlayerIdentifier> iter(&players_); !iter.IsAtEnd();
+       iter.Advance()) {
+    PlayerIdentifier* player_identifier = iter.GetCurrentValue();
+    if (delegate == player_identifier->delegate_)
+      players_.Remove(iter.GetCurrentKey());
+  }
+
+  AbandonAudioFocusIfNeeded();
+}
+
+void MediaSession::AbandonAudioFocusIfNeeded() {
+  if (!has_audio_focus_ || !players_.IsEmpty())
+    return;
+
+  JNIEnv* env = base::android::AttachCurrentThread();
+  DCHECK(env);
+  Java_MediaSession_abandonAudioFocus(env, j_media_session_.obj());
+  has_audio_focus_ = false;
+}
+
+void MediaSession::OnSuspend(JNIEnv* env, jobject obj) {
+  has_audio_focus_ = false;
+
+  for (PlayersMap::Iterator<PlayerIdentifier> iter(&players_); !iter.IsAtEnd();
+       iter.Advance()) {
+    PlayerIdentifier* player_identifier = iter.GetCurrentValue();
+    player_identifier->delegate_->OnSuspend(player_identifier->id_);
+  }
+}
+
+void MediaSession::OnResume(JNIEnv* env, jobject obj) {
+  has_audio_focus_ = true;
+
+  for (PlayersMap::Iterator<PlayerIdentifier> iter(&players_); !iter.IsAtEnd();
+       iter.Advance()) {
+    PlayerIdentifier* player_identifier = iter.GetCurrentValue();
+    player_identifier->delegate_->OnResume(player_identifier->id_);
+  }
+}
+
+}  // namespace content