Add static root property tree nodes [spv2]

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

Index: third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
diff --git a/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h b/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
index 293da8d1a609fe1671119034fd12bc65289ff095..4abae0cbd4814dab73a252faacd9c1a4e56ae2e4 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
+++ b/third_party/WebKit/Source/platform/graphics/paint/ClipPaintPropertyNode.h
@@ -42,6 +42,7 @@ public:
 
     // Reference to inherited clips, or nullptr if this is the only clip.
     const ClipPaintPropertyNode* parent() const { return m_parent.get(); }
+    bool isRoot() const { return !m_parent; }

[chrishtr, 2016/09/22 16:36:57]

You never use this method outside of tests. why add it?

[pdr., 2016/09/22 19:48:21]

It's also used in the property tree printer. I think we'll start using it for
real in the followup when root layer scrolls begins using the root nodes. For
example, we can dcheck that the root nodes aren't modified. We could do a
private/friend approach but I don't think we will want to hide the root node
concept.

 
 private:
     ClipPaintPropertyNode(PassRefPtr<const ClipPaintPropertyNode> parent, PassRefPtr<const TransformPaintPropertyNode> localTransformSpace, const FloatRoundedRect& clipRect)