Put transform tree building in DisplayItemPropertyTreeBuilder.

public/platform/WebDisplayItemClipTree.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 WebDisplayItemClipTree_h
+#define WebDisplayItemClipTree_h
+
+#include "public/platform/WebCommon.h"
+#include "public/platform/WebFloatRect.h"
+#include "public/platform/WebPrivateOwnPtr.h"
+
+namespace blink {
+
+class DisplayItemClipTree;
+
+// Represents a hierarchy of rectangular clips which apply to ranges of a
+// display list and may be of interest to the compositor.
+//
+// It consists of a tree of "transform nodes", stored in a flattened
+// representation in which their order is not guaranteed. Each node has a
+// parent (whose clip, and those of its ancestors, also apply to content),
+// a transform node index (into an associated |WebDisplayItemTransformTree|
+// which defines the coordinate space in which this clip is interpreted),
+// and a rectangle representing the clip.
+//
+// Rounded-rect clips are represented here by their bounding rect; the rounded
+// clip should be represented outside the clip tree (e.g. as a mask).
+class BLINK_PLATFORM_EXPORT WebDisplayItemClipTree {
+public:
+    enum : size_t { kInvalidIndex = static_cast<size_t>(-1) };
+
+    struct ClipNode {
+        ClipNode(size_t parent, size_t transformNodeIndex, const WebFloatRect& clipRect)
+            : parentNodeIndex(parent)
+            , transformNodeIndex(transformNodeIndex)
+            , clipRect(clipRect)
+        {
+        }
+
+        bool isRoot() const { return parentNodeIndex == kInvalidIndex; }
+
+        // Index of parent in m_nodes (kInvalidIndex for root).
+        size_t parentNodeIndex;
+
+        // Index of transform node in which this clip should be interpreted.
+        // Cannot be WebDisplayItemTransformTree::kInvalidIndex.
+        size_t transformNodeIndex;
+
+        // Rectangular clip in the space of the transform node.
+        WebFloatRect clipRect;
+    };
+
+    WebDisplayItemClipTree();
+#if INSIDE_BLINK
+    WebDisplayItemClipTree(const WTF::PassOwnPtr<DisplayItemClipTree>&);
+#endif
+
+    ~WebDisplayItemClipTree();
+
+    // Returns the number of nodes in the clip tree.
+    size_t nodeCount() const;
+
+    // Returns a node in the clip tree by its index (from 0 to nodeCount() - 1).
+    const ClipNode& nodeAt(size_t index) const;
+
+private:
+    WebPrivateOwnPtr<const DisplayItemClipTree> m_private;
+};
+
+} // namespace blink
+
+#endif // WebDisplayItemClipTree_h