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

Source/platform/graphics/paint/DisplayItemTransformTreeBuilder.h

Index: Source/platform/graphics/paint/DisplayItemTransformTreeBuilder.h
diff --git a/Source/platform/graphics/paint/DisplayItemTransformTreeBuilder.h b/Source/platform/graphics/paint/DisplayItemTransformTreeBuilder.h
index 70ca0bcbb9c37ee3279950c5030d711bdaa406df..be8489858dface46b573cf830b8b411f7feb04f2 100644
--- a/Source/platform/graphics/paint/DisplayItemTransformTreeBuilder.h
+++ b/Source/platform/graphics/paint/DisplayItemTransformTreeBuilder.h
@@ -7,6 +7,7 @@
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/FloatSize.h"
+#include "platform/graphics/paint/DisplayItemList.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/Vector.h"
@@ -14,7 +15,9 @@
 namespace blink {
 
 class DisplayItem;
+class DisplayItemList;
 class DisplayItemTransformTree;
+class WebDisplayList;
 
 class PLATFORM_EXPORT DisplayItemTransformTreeBuilder {
 public:
@@ -25,6 +28,8 @@ public:
     // This can be used to construct a WebDisplayItemTransformTree.
     PassOwnPtr<DisplayItemTransformTree> releaseTransformTree();
 
+    void build(const DisplayItemList& displayList, const DisplayListDiff&);

[weiliangc, 2015/07/24 19:17:15]

Would it make sense to make DisplayItemTransformTreeBuilder look more like
DisplayListCompositngBuilder?
Such as, set const & to displayList and displayListDiff in constructor, build(),
and hide and processDisplayItem() function?

[chrishtr, 2015/07/24 19:27:22]

Common patterns good yes. :)

+
     // Process another display item from the list.
     void processDisplayItem(const DisplayItem&);