Replace RenderArena with PartitionAlloc

Source/core/page/Page.h

Index: Source/core/page/Page.h
diff --git a/Source/core/page/Page.h b/Source/core/page/Page.h
index 870ff64674300eef28c0ecf16df788cc6e2685ba..0edf04d2ec839f8cd5f3735bc1acd2fa8180dd78 100644
--- a/Source/core/page/Page.h
+++ b/Source/core/page/Page.h
@@ -80,16 +80,6 @@ typedef uint64_t LinkHash;
 
 float deviceScaleFactor(Frame*);
 
-struct ArenaSize {
-    ArenaSize(size_t treeSize, size_t allocated)
-        : treeSize(treeSize)
-        , allocated(allocated)
-    {
-    }
-    size_t treeSize;
-    size_t allocated;
-};
-
 class Page : public Supplementable<Page>, public LifecycleContext {
     WTF_MAKE_NONCOPYABLE(Page);
     friend class Settings;
@@ -114,8 +104,6 @@ public:
     explicit Page(PageClients&);
     ~Page();
 
-    ArenaSize renderTreeSize() const;
-
     void setNeedsRecalcStyleInAllFrames();
 
     RenderTheme* theme() const { return m_theme.get(); }