Client side display item cache flag

third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.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 DisplayItemClient_h
 #define DisplayItemClient_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/IntRect.h"
 #include "wtf/text/WTFString.h"
@@ skipping 12 matching lines @@
     virtual ~DisplayItemClient();
 #else
     virtual ~DisplayItemClient() { }
 #endif
 
     virtual String debugName() const = 0;
 
     // The visual rect of this DisplayItemClient, in the space of its containing GraphicsLayer.
     virtual IntRect visualRect() const = 0;
 
+    static const unsigned kInvalidCacheGeneration = 0;
+
+    virtual bool displayItemsAreCached(unsigned cacheGeneration) const = 0;
+    virtual void setDisplayItemsCached(unsigned cacheGeneration) const = 0;
+
 #if ENABLE(ASSERT)
     // Tests if a DisplayItemClient object has been created and has not been deleted yet.
     static bool isAlive(const DisplayItemClient&);
 #endif
+
+protected:
+    // To make m_displayItemCacheGeneration (in DISPLAY_ITEM_CACHE_STATUS_IMPLEMENTATION)
+    // automatically initialized.
+    struct DisplayItemCacheGeneration {
+        DisplayItemCacheGeneration() : value(kInvalidCacheGeneration) { }
+        unsigned value;
+    };
 };
 
+#define DISPLAY_ITEM_CACHE_STATUS_IMPLEMENTATION \
+    bool displayItemsAreCached(unsigned cacheGeneration) const final { return cacheGeneration != kInvalidCacheGeneration && m_displayItemCacheGeneration.value == cacheGeneration; } \
+    void setDisplayItemsCached(unsigned cacheGeneration) const final { m_displayItemCacheGeneration.value = cacheGeneration; } \
+    mutable DisplayItemCacheGeneration m_displayItemCacheGeneration;
+
+#define DISPLAY_ITEM_CACHE_STATUS_UNCACHEABLE_IMPLEMENTATION \
+    bool displayItemsAreCached(unsigned cacheGeneration) const final { return false; } \
+    void setDisplayItemsCached(unsigned cacheGeneration) const final { }
+
 inline bool operator==(const DisplayItemClient& client1, const DisplayItemClient& client2) { return &client1 == &client2; }
 inline bool operator!=(const DisplayItemClient& client1, const DisplayItemClient& client2) { return &client1 != &client2; }
 
-}
+} // namespace blink
 
 #endif // DisplayItemClient_h