Introduce FragmentData, and put ObjectPaintProperties into it

This is a step towards supporting multicol in SPv2.

BUG=648274
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2

Review-Url: https://codereview.chromium.org/2844803007
Cr-Commit-Position: refs/heads/master@{#468207}

third_party/WebKit/Source/core/layout/LayoutObject.h

@@ -1810,7 +1810,9 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
     // The following non-const functions for ObjectPaintProperties should only
     // be called from PaintPropertyTreeBuilder.
     ObjectPaintProperties& EnsurePaintProperties() {
-      return layout_object_.EnsureRarePaintData().EnsurePaintProperties();
+      return layout_object_.EnsureRarePaintData()
+          .EnsureFragment()
+          .EnsurePaintProperties();
     }
     ObjectPaintProperties* PaintProperties() {
       if (auto* paint_data = layout_object_.GetRarePaintData())
@@ -1818,8 +1820,10 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
       return nullptr;
     }
     void ClearPaintProperties() {
-      if (auto* paint_data = layout_object_.GetRarePaintData())
-        paint_data->ClearPaintProperties();
+      if (auto* paint_data = layout_object_.GetRarePaintData()) {
+        if (auto* fragment = paint_data->Fragment())
+          fragment->ClearPaintProperties();
+      }
     }
 
     // The following non-const functions for local border box properties should

third_party/WebKit/Source/core/paint/BUILD.gn

@@ -56,6 +56,8 @@ blink_core_sources("paint") {
     "FirstMeaningfulPaintDetector.h",
     "FloatClipRecorder.cpp",
     "FloatClipRecorder.h",
+    "FragmentData.cpp",
+    "FragmentData.h",
     "FramePainter.cpp",
     "FramePainter.h",
     "FrameSetPainter.cpp",

third_party/WebKit/Source/core/paint/FragmentData.cpp

+// Copyright 2017 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.
+
+#include "core/paint/FragmentData.h"
+#include "core/paint/ObjectPaintProperties.h"
+
+namespace blink {
+
+ObjectPaintProperties& FragmentData::EnsurePaintProperties() {
+  if (!paint_properties_)
+    paint_properties_ = ObjectPaintProperties::Create();
+  return *paint_properties_.get();
+}
+
+void FragmentData::ClearPaintProperties() {
+  paint_properties_.reset(nullptr);
+}
+
+}  // namespace blink

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

+// Copyright 2017 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 FragmentData_h
+#define FragmentData_h
+
+#include "core/paint/ObjectPaintProperties.h"
+
+namespace blink {
+
+class ObjectPaintProperties;
+
+// Represents the data for a particular fragment of a LayoutObject.
+// Only LayoutObjects with a self-painting PaintLayer may have more than one
+// FragmentDeta, and even then only when they are inside of multicol.
+// See README.md.
+class CORE_EXPORT FragmentData {
+ public:
+  static std::unique_ptr<FragmentData> Create() {
+    return WTF::WrapUnique(new FragmentData());
+  }
+
+  ObjectPaintProperties* PaintProperties() const {
+    return paint_properties_.get();
+  }
+  ObjectPaintProperties& EnsurePaintProperties();
+  void ClearPaintProperties();
+
+  FragmentData* NextFragment() { return next_fragment_.get(); }
+
+ private:
+  // Holds references to the paint property nodes created by this object.
+  std::unique_ptr<ObjectPaintProperties> paint_properties_;
+
+  std::unique_ptr<FragmentData> next_fragment_;
+};
+
+}  // namespace blink
+
+#endif  // FragmentData_h

third_party/WebKit/Source/core/paint/RarePaintData.cpp

@@ -4,7 +4,7 @@
 
 #include "core/paint/RarePaintData.h"
 
-#include "core/paint/ObjectPaintProperties.h"
+#include "core/paint/FragmentData.h"
 #include "core/paint/PaintLayer.h"
 
 namespace blink {
@@ -17,14 +17,10 @@ void RarePaintData::SetLayer(std::unique_ptr<PaintLayer> layer) {
   layer_ = std::move(layer);
 };
 
-ObjectPaintProperties& RarePaintData::EnsurePaintProperties() {
-  if (!paint_properties_)
-    paint_properties_ = ObjectPaintProperties::Create();
-  return *paint_properties_.get();
-}
-
-void RarePaintData::ClearPaintProperties() {
-  paint_properties_.reset(nullptr);
+FragmentData& RarePaintData::EnsureFragment() {
+  if (!fragment_data_)
+    fragment_data_ = FragmentData::Create();
+  return *fragment_data_.get();
 }
 
 void RarePaintData::ClearLocalBorderBoxProperties() {
@@ -41,13 +37,15 @@ void RarePaintData::SetLocalBorderBoxProperties(PropertyTreeState& state) {
 PropertyTreeState RarePaintData::ContentsProperties() const {
   DCHECK(local_border_box_properties_);
   PropertyTreeState contents(*local_border_box_properties_);
-  if (paint_properties_) {
-    if (paint_properties_->ScrollTranslation())
-      contents.SetTransform(paint_properties_->ScrollTranslation());
-    if (paint_properties_->OverflowClip())
-      contents.SetClip(paint_properties_->OverflowClip());
-    else if (paint_properties_->CssClip())
-      contents.SetClip(paint_properties_->CssClip());
+  if (fragment_data_) {
+    if (auto* properties = fragment_data_->PaintProperties()) {
+      if (properties->ScrollTranslation())
+        contents.SetTransform(properties->ScrollTranslation());
+      if (properties->OverflowClip())
+        contents.SetClip(properties->OverflowClip());
+      else if (properties->CssClip())
+        contents.SetClip(properties->CssClip());
+    }
   }
 
   // TODO(chrishtr): cssClipFixedPosition needs to be handled somehow.

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

@@ -6,13 +6,13 @@
 #define RarePaintData_h
 
 #include "core/CoreExport.h"
+#include "core/paint/FragmentData.h"
 #include "platform/wtf/Allocator.h"
 #include "platform/wtf/Noncopyable.h"
 
 namespace blink {
 
 class PropertyTreeState;
-class ObjectPaintProperties;
 class PaintLayer;
 
 // This is for paint-related data on LayoutObject that is not needed on all
@@ -28,11 +28,15 @@ class CORE_EXPORT RarePaintData {
   PaintLayer* Layer() { return layer_.get(); }
   void SetLayer(std::unique_ptr<PaintLayer>);
 
+  FragmentData* Fragment() const { return fragment_data_.get(); }
+
+  FragmentData& EnsureFragment();
+
   ObjectPaintProperties* PaintProperties() const {
-    return paint_properties_.get();
+    if (fragment_data_)
+      return fragment_data_->PaintProperties();
+    return nullptr;
   }
-  ObjectPaintProperties& EnsurePaintProperties();
-  void ClearPaintProperties();
 
   PropertyTreeState* LocalBorderBoxProperties() const {
     return local_border_box_properties_.get();
@@ -52,8 +56,7 @@ class CORE_EXPORT RarePaintData {
   // depending on the return value of LayoutBoxModelObject::layerTypeRequired().
   std::unique_ptr<PaintLayer> layer_;
 
-  // Holds references to the paint property nodes created by this object.
-  std::unique_ptr<ObjectPaintProperties> paint_properties_;
+  std::unique_ptr<FragmentData> fragment_data_;
 
   // This is a complete set of property nodes that should be used as a
   // starting point to paint a LayoutObject. This data is cached because some