Change various helper classes to transition types to get CSSValue entirely onto the gc heap.

Source/core/css/MediaList.cpp

Index: Source/core/css/MediaList.cpp
diff --git a/Source/core/css/MediaList.cpp b/Source/core/css/MediaList.cpp
index 11ae84b35d4a9b81b01b72d0a684dbc8633b60ca..bb67daa4d44474f6e91f3ca4faac58bd2a8db6bf 100644
--- a/Source/core/css/MediaList.cpp
+++ b/Source/core/css/MediaList.cpp
@@ -52,13 +52,15 @@ namespace WebCore {
  * CSS 3 Media Queries Spec (http://www.w3.org/TR/css3-mediaqueries/)
  */
 
+DEFINE_GC_INFO(MediaQuerySet);
+DEFINE_GC_INFO(MediaList);
+
 MediaQuerySet::MediaQuerySet()
 {
 }
 
 MediaQuerySet::MediaQuerySet(const MediaQuerySet& o)
-    : RefCounted<MediaQuerySet>()
-    , m_queries(o.m_queries.size())
+    : m_queries(o.m_queries.size())
 {
     for (unsigned i = 0; i < m_queries.size(); ++i)
         m_queries[i] = o.m_queries[i]->copy();
@@ -68,7 +70,7 @@ MediaQuerySet::~MediaQuerySet()
 {
 }
 
-PassRefPtr<MediaQuerySet> MediaQuerySet::create(const String& mediaString)
+PassRefPtrWillBeRawPtr<MediaQuerySet> MediaQuerySet::create(const String& mediaString)
 {
     if (mediaString.isEmpty())
         return MediaQuerySet::create();
@@ -79,7 +81,7 @@ PassRefPtr<MediaQuerySet> MediaQuerySet::create(const String& mediaString)
 
 bool MediaQuerySet::set(const String& mediaString)
 {
-    RefPtr<MediaQuerySet> result = create(mediaString);
+    RefPtrWillBeRawPtr<MediaQuerySet> result = create(mediaString);
     m_queries.swap(result->m_queries);
     return true;
 }
@@ -89,13 +91,13 @@ bool MediaQuerySet::add(const String& queryString)
     // To "parse a media query" for a given string means to follow "the parse
     // a media query list" steps and return "null" if more than one media query
     // is returned, or else the returned media query.
-    RefPtr<MediaQuerySet> result = create(queryString);
+    RefPtrWillBeRawPtr<MediaQuerySet> result = create(queryString);
 
     // Only continue if exactly one media query is found, as described above.
     if (result->m_queries.size() != 1)
         return true;
 
-    OwnPtr<MediaQuery> newQuery = result->m_queries[0].release();
+    OwnPtrWillBeRawPtr<MediaQuery> newQuery = result->m_queries[0].release();
     ASSERT(newQuery);
 
     // If comparing with any of the media queries in the collection of media
@@ -115,13 +117,13 @@ bool MediaQuerySet::remove(const String& queryStringToRemove)
     // To "parse a media query" for a given string means to follow "the parse
     // a media query list" steps and return "null" if more than one media query
     // is returned, or else the returned media query.
-    RefPtr<MediaQuerySet> result = create(queryStringToRemove);
+    RefPtrWillBeRawPtr<MediaQuerySet> result = create(queryStringToRemove);
 
     // Only continue if exactly one media query is found, as described above.
     if (result->m_queries.size() != 1)
         return true;
 
-    OwnPtr<MediaQuery> newQuery = result->m_queries[0].release();
+    OwnPtrWillBeRawPtr<MediaQuery> newQuery = result->m_queries[0].release();
     ASSERT(newQuery);
 
     // Remove any media query from the collection of media queries for which
@@ -139,7 +141,7 @@ bool MediaQuerySet::remove(const String& queryStringToRemove)
     return found;
 }
 
-void MediaQuerySet::addMediaQuery(PassOwnPtr<MediaQuery> mediaQuery)
+void MediaQuerySet::addMediaQuery(PassOwnPtrWillBeRawPtr<MediaQuery> mediaQuery)
 {
     m_queries.append(mediaQuery);
 }
@@ -159,6 +161,15 @@ String MediaQuerySet::mediaText() const
     return text.toString();
 }
 
+void MediaQuerySet::trace(Visitor* visitor)
+{
+    // We don't support tracing of vectors of OwnPtrs (ie. OwnPtr<Vector<OwnPtr<MediaQuery> > >).

[haraken, 2014/02/21 01:02:36]

OwnPtr<Vector<OwnPtr<MediaQuery> > > => Vector<OwnPtr<MediaQuery> >

Can we add a dummy trace for Vector<OwnPtr> and avoid adding ENABLE(OILPAN) ?

[wibling-chromium, 2014/02/21 08:43:08]

We talked a bit about this locally. We could fix the OffHeapCollectionTrait to
call the visitor->trace instead of calling the tracetrait. That would make it
work AFAICT. I will do a bit of experimenting locally with the oilpan branch to
see if that fixes the issue.
This would basically allow us to support tracing of Vector's of ownptrs
independent of whether oilpan flag is enabled.

If I instead add a dummy trace trait it would mean we could not support tracing
vector's of ownptrs even in the case where e.g. the modules wanted to do that.

[wibling-chromium, 2014/02/25 12:07:28]

I tried this above and both when calling visitor->trace in the
OffHeapCollectionTrait and when defining a dummy TraceTrait for the OwnPtr I got
into problems with the DefaultAllocatorDummyVisitor class defined in WTF and
that it was not assignable to the WebCore::Visitor class. I will leave the
ifdef's in for now and we can see if we come up with something clever in the
future.
This should go away together with the transition types.

[haraken, 2014/02/25 12:09:57]

Makes sense. Having #if in a couple of places in a transition period wouldn't be
a big deal.

+    // Since this is a transitional object we are just ifdef'ing it out when oilpan is not enabled.
+#if ENABLE(OILPAN)
+    visitor->trace(m_queries);
+#endif
+}
+
 MediaList::MediaList(MediaQuerySet* mediaQueries, CSSStyleSheet* parentSheet)
     : m_mediaQueries(mediaQueries)
     , m_parentStyleSheet(parentSheet)
@@ -189,7 +200,7 @@ void MediaList::setMediaText(const String& value)
 
 String MediaList::item(unsigned index) const
 {
-    const Vector<OwnPtr<MediaQuery> >& queries = m_mediaQueries->queryVector();
+    const WillBeHeapVector<OwnPtrWillBeMember<MediaQuery> >& queries = m_mediaQueries->queryVector();
     if (index < queries.size())
         return queries[index]->cssText();
     return String();
@@ -228,6 +239,11 @@ void MediaList::reattach(MediaQuerySet* mediaQueries)
     m_mediaQueries = mediaQueries;
 }
 
+void MediaList::trace(Visitor* visitor)
+{
+    visitor->trace(m_mediaQueries);
+}
+
 static void addResolutionWarningMessageToConsole(Document* document, const String& serializedExpression, const CSSPrimitiveValue* value)
 {
     ASSERT(document);
@@ -264,7 +280,7 @@ void reportMediaQueryWarningIfNeeded(Document* document, const MediaQuerySet* me
     if (!mediaQuerySet || !document)
         return;
 
-    const Vector<OwnPtr<MediaQuery> >& mediaQueries = mediaQuerySet->queryVector();
+    const WillBeHeapVector<OwnPtrWillBeMember<MediaQuery> >& mediaQueries = mediaQuerySet->queryVector();
     const size_t queryCount = mediaQueries.size();
 
     if (!queryCount)