SPv2: Use GeometryMapper to implement PaintLayerClipper.

third_party/WebKit/Source/core/paint/PaintLayerClipper.h

Index: third_party/WebKit/Source/core/paint/PaintLayerClipper.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerClipper.h b/third_party/WebKit/Source/core/paint/PaintLayerClipper.h
index c3ad800e810459a338fe16444bad878dd48d51ef..4081b8db95cc9743a84200d7b387fe690584e377 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerClipper.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayerClipper.h
@@ -48,6 +48,12 @@
 #include "core/CoreExport.h"
 #include "core/layout/ClipRectsCache.h"
 #include "core/layout/ScrollEnums.h"
+
+#include "platform/graphics/paint/ClipPaintPropertyNode.h"

[Xianzhu, 2016/08/15 17:09:04]

Nit: The XXXPaintPropertyNode.h headers are actually required by
PropertyTreeState.h so they should be included in that file.
https://codereview.chromium.org/2238853005/ does that.

[chrishtr, 2016/10/05 23:28:32]

Done.

+#include "platform/graphics/paint/EffectPaintPropertyNode.h"
+#include "platform/graphics/paint/GeometryMapper.h"
+#include "platform/graphics/paint/TransformPaintPropertyNode.h"
+
 #include "wtf/Allocator.h"
 
 namespace blink {
@@ -106,6 +112,20 @@ private:
 // PaintLayerClipper is responsible for computing and caching clip
 // rects.
 //
+// These clip rects have two types: background and foreground.
+//
+// The "background rect" for a PaintLayer is almost the same as its visual
+// rect in the space of some ancestor PaintLayer (specified by a parameter).
+// The only difference is that unclipped rect at the start is LayoutRect::infiniteIntRect,
+// rather than the local overflow bounds of the PaintLayer. Thus, for example
+// if there are no clips then the background rect will be infinite.
+// Also, whether overflow clip of the ancestor should be applied is a parameter.
+//
+// The "foreground rect" for a PaintLayer is its "background rect", intersected
+// with any clip applied by this PaintLayer to its children.
+
+// Motivation for this class:
+//
 // The main reason for this cache is that we compute the clip rects during
 // a layout tree walk but need them during a paint tree walk (see example
 // below for some explanations).
@@ -151,7 +171,7 @@ private:
 class CORE_EXPORT PaintLayerClipper {
     DISALLOW_NEW();
 public:
-    explicit PaintLayerClipper(const PaintLayer& layer) : m_layer(layer) { }
+    explicit PaintLayerClipper(const PaintLayer&);
 
     void clearClipRectsIncludingDescendants();
     void clearClipRectsIncludingDescendants(ClipRectsCacheSlot);
@@ -181,7 +201,10 @@ private:
 
     bool shouldRespectOverflowClip(const ClipRectsContext&) const;
 
+    ClipRect clipRectWithGeometryMapper(const ClipRectsContext&, bool isForeground) const;
+
     const PaintLayer& m_layer;
+    std::unique_ptr<GeometryMapper> m_geometryMapper;
 };
 
 } // namespace blink