Slimming Paint phase 2 compositing algorithm plumbing & skeleton display list API.

Source/platform/graphics/paint/DisplayItemList.h

Index: Source/platform/graphics/paint/DisplayItemList.h
diff --git a/Source/platform/graphics/paint/DisplayItemList.h b/Source/platform/graphics/paint/DisplayItemList.h
index 133e2f8e0b18840e0b0b2a9cdfefe8b825098e20..5790fff933ba2409a71aafc27424d555d55a3f24 100644
--- a/Source/platform/graphics/paint/DisplayItemList.h
+++ b/Source/platform/graphics/paint/DisplayItemList.h
@@ -9,6 +9,7 @@
 #include "platform/graphics/ListContainer.h"
 #include "platform/graphics/paint/DisplayItem.h"
 #include "platform/graphics/paint/Transform3DDisplayItem.h"
+#include "public/platform/WebDisplayList.h"
 #include "wtf/HashMap.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/Utility.h"
@@ -23,7 +24,7 @@ using DisplayItems = ListContainer<DisplayItem>;
 static const size_t kInitialDisplayItemsCapacity = 64;
 static const size_t kMaximumDisplayItemSize = sizeof(BeginTransform3DDisplayItem);
 
-class PLATFORM_EXPORT DisplayItemList {
+class PLATFORM_EXPORT DisplayItemList : public WebDisplayList {
     WTF_MAKE_NONCOPYABLE(DisplayItemList);
     WTF_MAKE_FAST_ALLOCATED(DisplayItemList);
 public:
@@ -52,6 +53,8 @@ public:
     void beginScope(DisplayItemClient);
     void endScope(DisplayItemClient);
 
+    void addPixelRef(const skia::PixelRefUtils::PositionPixelRef&);
+
     // True if the last display item is a begin that doesn't draw content.
     bool lastDisplayItemIsNoopBegin() const;
     void removeLastDisplayItem();
@@ -60,8 +63,9 @@ public:
     void endSkippingCache() { ASSERT(m_skippingCacheCount > 0); --m_skippingCacheCount; }
     bool skippingCache() const { return m_skippingCacheCount; }
 
-    // Must be called when a painting is finished.
-    void commitNewDisplayItems();
+    // Must be called when a painting is finished. If passed, the diff is initialized
+    // to the difference of the new display list from the last time commitNewDisplayItems() was called.
+    void commitNewDisplayItems(WebDisplayListDiff* = 0);
 
     // Returns the approximate memory usage, excluding memory likely to be
     // shared with the embedder after copying to WebDisplayItemList.
@@ -70,6 +74,9 @@ public:
 
     // Get the paint list generated after the last painting.
     const DisplayItems& displayItems() const;
+    const WebVector<WebDisplayItem>& webDisplayItems() const override;
+    // Get the pixel refs generated after the last painting.
+    const skia::DiscardablePixelRefList& pixelRefs() const override;
 
     bool clientCacheIsValid(DisplayItemClient) const;
 
@@ -165,12 +172,18 @@ private:
     ClientScopeIdMap m_clientScopeIdMap;
     Vector<Scope> m_scopeStack;
 
+    skia::DiscardablePixelRefList m_currentPixelRefs;
+    skia::DiscardablePixelRefList m_newPixelRefs;
+
 #if ENABLE(ASSERT)
     // This is used to check duplicated ids during add(). We could also check during
     // updatePaintList(), but checking during add() helps developer easily find where
     // the duplicated ids are from.
     DisplayItemIndicesByClientMap m_newDisplayItemIndicesByClient;
 #endif
+
+    // This is a placeholder, not a real data structure.
+    WebVector<WebDisplayItem> m_webDisplayItems;
 };
 
 } // namespace blink