[Slimming Paint] Blink-side contiguous allocation of display items.

Source/platform/graphics/paint/DisplayItem.h

 // Copyright 2014 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 DisplayItem_h
 #define DisplayItem_h
 
 #include "platform/PlatformExport.h"
 #include "platform/graphics/paint/DisplayItemClient.h"
 #include "wtf/Assertions.h"
 #include "wtf/PassOwnPtr.h"
 
 #ifndef NDEBUG
 #include "wtf/text/StringBuilder.h"
 #include "wtf/text/WTFString.h"
 #endif
 
 
 namespace blink {
 
+class DisplayItems;
 class GraphicsContext;
 class WebDisplayItemList;
 
 class PLATFORM_EXPORT DisplayItem {
 public:
     enum {
         // Must be kept in sync with core/layout/PaintPhase.h.
         PaintPhaseMax = 12,
     };
 
@@ skipping 195 matching lines @@
     {
         m_scopeId = scopeId;
         m_scopeContainer = scopeContainer;
     }
 
     // For DisplayItemList only. Painters should use DisplayItemCacheSkipper instead.
     void setSkippedCache() { m_skippedCache = true; }
     bool skippedCache() const { return m_skippedCache; }
 
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const { }
+    virtual void appendByMoving(DisplayItems&) = 0;
 
     // See comments of enum Type for usage of the following macros.
 #define DEFINE_CATEGORY_METHODS(Category) \
     static bool is##Category##Type(Type type) { return type >= Category##First && type <= Category##Last; } \
     bool is##Category() const { return is##Category##Type(type()); }
 
 #define DEFINE_CONVERSION_METHODS(Category1, category1, Category2, category2) \
     static Type category1##TypeTo##Category2##Type(Type type) \
     { \
         static_assert(Category1##Last - Category1##First == Category2##Last - Category2##First, \
@@ skipping 80 matching lines @@
     const DisplayItemClient m_client;
     DisplayItemClient m_scopeContainer;
     int m_scopeId;
     static_assert(TypeLast < (1 << 16), "DisplayItem::Type should fit in 16 bits");
     const Type m_type : 16;
     unsigned m_skippedCache : 1;
 
 #ifndef NDEBUG
     WTF::String m_clientDebugString;
 #endif
+
+    // TODO(jbroman): Copying this data in appendByMoving would be better than
+    // friendship, but this is just hacked up.
+    friend class DisplayItems;
 };
 
 class PLATFORM_EXPORT PairedBeginDisplayItem : public DisplayItem {
 protected:
     PairedBeginDisplayItem(const DisplayItemClientWrapper& client, Type type) : DisplayItem(client, type) { }
 
 private:
     virtual bool isBegin() const override final { return true; }
 };
 
 class PLATFORM_EXPORT PairedEndDisplayItem : public DisplayItem {
 protected:
     PairedEndDisplayItem(const DisplayItemClientWrapper& client, Type type) : DisplayItem(client, type) { }
 
 #if ENABLE(ASSERT)
     virtual bool isEndAndPairedWith(DisplayItem::Type otherType) const override = 0;
 #endif
 
 private:
     virtual bool isEnd() const override final { return true; }
 };
 
+// Allows a DisplayItemClientWrapper to be constructed from a DisplayItem, in
+// order to facilitate copying it.
+// TODO(jbroman): This is a bad class name.
+class DisplayItemClientWrapperHelper {
+    DISALLOW_ALLOCATION();
+public:
+    DisplayItemClientWrapperHelper(const DisplayItem& wrapped) : m_wrapped(wrapped) { }
+    DisplayItemClient displayItemClient() const { return m_wrapped.client(); }
+    String debugName() const
+    {
+#ifndef NDEBUG
+        return m_wrapped.clientDebugString();
+#else
+        return String();
+#endif
+    }
+private:
+    const DisplayItem& m_wrapped;
+};
+
+
 } // namespace blink
 
 #endif // DisplayItem_h