Oilpan: add transition types to track interface objects.

Source/core/html/track/TextTrack.cpp

Index: Source/core/html/track/TextTrack.cpp
diff --git a/Source/core/html/track/TextTrack.cpp b/Source/core/html/track/TextTrack.cpp
index 5789476a8f848fd66ba5818692bb11e87bcb4c15..4c5de8448173c4444c5ef8b8c0d2cb500d262b02 100644
--- a/Source/core/html/track/TextTrack.cpp
+++ b/Source/core/html/track/TextTrack.cpp
@@ -100,7 +100,7 @@ TextTrack::TextTrack(Document& document, const AtomicString& kind, const AtomicS
     , m_cues(nullptr)
     , m_regions(nullptr)
     , m_document(&document)
-    , m_trackList(0)
+    , m_trackList(nullptr)
     , m_mode(disabledKeyword())
     , m_trackType(type)
     , m_readinessState(NotLoaded)
@@ -114,6 +114,7 @@ TextTrack::TextTrack(Document& document, const AtomicString& kind, const AtomicS
 
 TextTrack::~TextTrack()
 {
+#if !ENABLE(OILPAN)
     ASSERT(!m_trackList);
 
     if (m_cues) {
@@ -125,6 +126,7 @@ TextTrack::~TextTrack()
         for (size_t i = 0; i < m_regions->length(); ++i)
             m_regions->item(i)->setTrack(0);
     }

[haraken, 2014/04/21 01:30:54]

Actually I don't fully understand the relationship between TextTrack,
TextTrackCueList and VTTRegionList, and thus it's not clear to me if it's OK to
just comment out the setTrack(0)s from the destructor. Would you elaborate on it
for me?

[sof, 2014/04/21 15:23:42]

Cues and regions for a text track are explicitly added and removed from this
list. They maintain a strong reference back to their list, which is cleared when
they're explicitly remove()d.

Consequently, not clearing them is fine, as they'll be destructed together.

For similar reasons, m_trackList doesn't have to be checked for being empty or
not in the Oilpan case. If it is null, then the TextTrack has been removed from
a TextTrackList. If it is non-null, then the TextTrack object is being
finalized/destructed at the same time as its TextTrackList parent.

A TextTrackList persistent reference is kept by a media element. And as it
explicitly clears itself as an owner of the TextTrackList, by the time this
destructor (and that for TextTrackList) gets to run, the effect of calling e.g.
setTrack(0) is effectively a no-op, it has been detached from the media element
and won't cause any updates.

[haraken, 2014/04/22 02:37:47]

Thanks for the detailed explanation. You explanation makes sense, but does it
mean that we don't need the code (line 118 - 127) even in non-oilpan builds? If
TextTrackList and TextTracks in the list die together, we won't need to
explicitly call setTrack(0).

[sof, 2014/04/22 06:27:51]

That is a good observation. As the pointers in the reverse direction are just
raw pointers in the non-Oilpan case, clearing them out has no practical function
at this stage. And we're already letting go of the ref pointers in the other
direction to release the track & cue objects, so no further work needed here.

Removed these two loops + #if.

+#endif
 }
 
 bool TextTrack::isValidKindKeyword(const AtomicString& value)
@@ -224,12 +226,12 @@ TextTrackCueList* TextTrack::activeCues() const
     return 0;
 }
 
-void TextTrack::addCue(PassRefPtr<TextTrackCue> prpCue)
+void TextTrack::addCue(PassRefPtrWillBeRawPtr<TextTrackCue> prpCue)
 {
     if (!prpCue)
         return;
 
-    RefPtr<TextTrackCue> cue = prpCue;
+    RefPtrWillBeRawPtr<TextTrackCue> cue = prpCue;
 
     // TODO(93143): Add spec-compliant behavior for negative time values.
     if (std::isnan(cue->startTime()) || std::isnan(cue->endTime()) || cue->startTime() < 0 || cue->endTime() < 0)
@@ -301,12 +303,12 @@ VTTRegionList* TextTrack::regions()
     return 0;
 }
 
-void TextTrack::addRegion(PassRefPtr<VTTRegion> prpRegion)
+void TextTrack::addRegion(PassRefPtrWillBeRawPtr<VTTRegion> prpRegion)
 {
     if (!prpRegion)
         return;
 
-    RefPtr<VTTRegion> region = prpRegion;
+    RefPtrWillBeRawPtr<VTTRegion> region = prpRegion;
     VTTRegionList* regionList = ensureVTTRegionList();
 
     // 1. If the given region is in a text track list of regions, then remove
@@ -433,4 +435,12 @@ HTMLMediaElement* TextTrack::mediaElement()
     return m_trackList ? m_trackList->owner() : 0;
 }
 
+void TextTrack::trace(Visitor* visitor)
+{
+    visitor->trace(m_cues);
+    visitor->trace(m_regions);
+    visitor->trace(m_trackList);
+    TrackBase::trace(visitor);
+}
+
 } // namespace WebCore