Oilpan: Fix leaks through RenderStyle objects.

Source/core/css/CSSFontSelector.h

Index: Source/core/css/CSSFontSelector.h
diff --git a/Source/core/css/CSSFontSelector.h b/Source/core/css/CSSFontSelector.h
index 2ae019dd6241f8ed01ed53a0be80322b6ab5698a..a148384721ebd92296f789580a547e60a226f48d 100644
--- a/Source/core/css/CSSFontSelector.h
+++ b/Source/core/css/CSSFontSelector.h
@@ -86,7 +86,10 @@ private:
 
     void dispatchInvalidationCallbacks();
 
-    RawPtrWillBeMember<Document> m_document;
+    // FIXME: Oilpan: Ideally this should just be a traced Member but that will
+    // currently leak because RenderStyle and its data are not on the heap.
+    // See crbug.com/383860 for details.
+    RawPtrWillBeWeakMember<Document> m_document;
     // FIXME: Move to Document or StyleEngine.
     FontFaceCache m_fontFaceCache;
     WillBeHeapHashSet<RawPtrWillBeWeakMember<CSSFontSelectorClient> > m_clients;