Oilpan: turn StyleResourceLoader into a traced part object.

Source/core/css/resolver/StyleResourceLoader.cpp

Index: Source/core/css/resolver/StyleResourceLoader.cpp
diff --git a/Source/core/css/resolver/StyleResourceLoader.cpp b/Source/core/css/resolver/StyleResourceLoader.cpp
index a3cf753f69379d54c4e20a8ac341b82d063e2c38..edfa342025a447808aed9bcd47b581e2acc89ab6 100644
--- a/Source/core/css/resolver/StyleResourceLoader.cpp
+++ b/Source/core/css/resolver/StyleResourceLoader.cpp
@@ -46,6 +46,11 @@ StyleResourceLoader::StyleResourceLoader(Document* document)
 {
 }
 
+DEFINE_TRACE(StyleResourceLoader)
+{
+    visitor->trace(m_document);
+}
+
 void StyleResourceLoader::loadPendingSVGDocuments(LayoutStyle* layoutStyle, ElementStyleResources& elementStyleResources)
 {
     if (!layoutStyle->hasFilter() || elementStyleResources.pendingSVGDocuments().isEmpty())