Simplify subtree (now subsequence) caching

Source/platform/graphics/paint/SubtreeDisplayItem.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SubtreeDisplayItem_h
 #define SubtreeDisplayItem_h
 
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/paint/DisplayItem.h"
 #include "wtf/Assertions.h"
 
 namespace blink {
 
 class BeginSubtreeDisplayItem final : public PairedBeginDisplayItem {
 public:
-    BeginSubtreeDisplayItem(const DisplayItemClientWrapper& client, Type type)
-        : PairedBeginDisplayItem(client, type, sizeof(*this))
-    {
-        ASSERT(isBeginSubtreeType(type));
-    }
+    BeginSubtreeDisplayItem(const DisplayItemClientWrapper& client)
+        : PairedBeginDisplayItem(client, BeginSubtree, sizeof(*this))
+    { }
 };
 
 class EndSubtreeDisplayItem final : public PairedEndDisplayItem {
 public:
-    EndSubtreeDisplayItem(const DisplayItemClientWrapper& client, Type type)
-        : PairedEndDisplayItem(client, type, sizeof(*this))
-    {
-        ASSERT(isEndSubtreeType(type));
-    }
+    EndSubtreeDisplayItem(const DisplayItemClientWrapper& client)
+        : PairedEndDisplayItem(client, EndSubtree, sizeof(*this))
+    { }
 
 #if ENABLE(ASSERT)
-    bool isEndAndPairedWith(DisplayItem::Type otherType) const final { return DisplayItem::isBeginSubtreeType(otherType); }
+    bool isEndAndPairedWith(DisplayItem::Type otherType) const final { return otherType == BeginSubtree; }
 #endif
 };
 
 } // namespace blink
 
 #endif // SubtreeDisplayItem_h