Web Animations: Sort Players in DocumentTimeline::serviceAnimations

This patch makes Animations get serviced in the order specified by the
spec[1]. This means that once custom effect are implemented, they will
be queued up in the correct order. This also gets us closer to having
the animation stack in a correct order (I'm thinking of emptying the
stack after getting out the compositable values, as we traverse the
animations in the correct order).

[1] http://dev.w3.org/fxtf/web-animations/#the-animation-stack

BUG=334936

Review URL: https://codereview.chromium.org/185593010

git-svn-id: svn://svn.chromium.org/blink/trunk@168597 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/animation/DocumentTimeline.cpp

@@ -95,15 +95,19 @@ void DocumentTimeline::serviceAnimations()
     m_timing->cancelWake();
 
     double timeToNextEffect = std::numeric_limits<double>::infinity();
-    Vector<Player*> playersToRemove;
-    for (HashSet<RefPtr<Player> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it) {
-        Player* player = it->get();
-        if (!player->update())
-            playersToRemove.append(player);
-        timeToNextEffect = std::min(timeToNextEffect, player->timeToEffectChange());
+    Vector<Player*> players;
+    for (HashSet<RefPtr<Player> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it)
+        players.append(it->get());
+
+    std::sort(players.begin(), players.end(), Player::hasLowerPriority);
+
+    for (size_t i = 0; i < players.size(); ++i) {
+        Player* player = players[i];
+        if (player->update())
+            timeToNextEffect = std::min(timeToNextEffect, player->timeToEffectChange());
+        else
+            m_playersNeedingUpdate.remove(player);
     }
-    for (size_t i = 0; i < playersToRemove.size(); ++i)
-        m_playersNeedingUpdate.remove(playersToRemove[i]);
 
     ASSERT(!m_playersNeedingUpdate.isEmpty() || timeToNextEffect == std::numeric_limits<double>::infinity());
     if (timeToNextEffect < s_minimumDelay)

third_party/WebKit/Source/core/animation/Player.cpp

@@ -36,6 +36,16 @@
 
 namespace WebCore {
 
+namespace {
+
+static unsigned nextSequenceNumber()
+{
+    static unsigned next = 0;
+    return ++next;
+}
+
+}
+
 PassRefPtr<Player> Player::create(DocumentTimeline& timeline, TimedItem* content)
 {
     return adoptRef(new Player(timeline, content));
@@ -52,6 +62,7 @@ Player::Player(DocumentTimeline& timeline, TimedItem* content)
     , m_held(false)
     , m_isPausedForTesting(false)
     , m_outdated(false)
+    , m_sequenceNumber(nextSequenceNumber())
 {
     if (m_content) {
         if (m_content->player())
@@ -299,6 +310,17 @@ void Player::cancel()
     m_content = nullptr;
 }
 
+bool Player::hasLowerPriority(Player* player1, Player* player2)
+{
+    if (player1->m_startTime < player2->m_startTime)
+        return true;
+    if (player1->m_startTime > player2->m_startTime)
+        return false;
+    if (isNull(player1->m_startTime) != isNull(player2->m_startTime))
+        return isNull(player1->m_startTime);
+    return player1->m_sequenceNumber < player2->m_sequenceNumber;
+}
+
 void Player::pauseForTesting(double pauseTime)
 {
     RELEASE_ASSERT(!paused());

third_party/WebKit/Source/core/animation/Player.h

@@ -96,6 +96,8 @@ public:
     void cancelAnimationOnCompositor();
     bool hasActiveAnimationsOnCompositor();
 
+    static bool hasLowerPriority(Player*, Player*);
+
 private:
     Player(DocumentTimeline&, TimedItem*);
     double sourceEnd() const;
@@ -121,6 +123,8 @@ private:
 
     // This indicates timing information relevant to the player has changed
     bool m_outdated;
+
+    unsigned m_sequenceNumber;
 };
 
 } // namespace

third_party/WebKit/Source/core/animation/PlayerTest.cpp

@@ -679,4 +679,30 @@ TEST_F(AnimationPlayerTest, AttachedPlayers)
     EXPECT_TRUE(element->activeAnimations()->players().isEmpty());
 }
 
+TEST_F(AnimationPlayerTest, HasLowerPriority)
+{
+    // Note that start time defaults to null
+    RefPtr<Player> player1 = timeline->createPlayer(0);
+    RefPtr<Player> player2 = timeline->createPlayer(0);
+    player2->setStartTime(10);
+    RefPtr<Player> player3 = timeline->createPlayer(0);
+    RefPtr<Player> player4 = timeline->createPlayer(0);
+    player4->setStartTime(20);
+    RefPtr<Player> player5 = timeline->createPlayer(0);
+    player5->setStartTime(10);
+    RefPtr<Player> player6 = timeline->createPlayer(0);
+    player6->setStartTime(-10);
+    Vector<RefPtr<Player> > players;
+    players.append(player1);
+    players.append(player3);
+    players.append(player6);
+    players.append(player2);
+    players.append(player5);
+    players.append(player4);
+    for (size_t i = 0; i < players.size(); i++) {
+        for (size_t j = 0; j < players.size(); j++)
+            EXPECT_EQ(i < j, Player::hasLowerPriority(players[i].get(), players[j].get()));
+    }
+}
+
 }