Client side display item cache flag

third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.h

Index: third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.h
diff --git a/third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.h b/third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.h
index 118ac51dc755dbcb015e2d13318043ae8163f787..e8fc1a5652f3a021e4841088e3f678821deca5b7 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.h
+++ b/third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.h
@@ -30,15 +30,37 @@ public:
     // 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