Generate scroll/clip display item hierarchy for SPv2

Source/core/paint/BoxClipper.cpp

 // Copyright 2014 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 "config.h"
 #include "core/paint/BoxClipper.h"
 
 #include "core/layout/LayoutBox.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/paint/PaintInfo.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/ClipDisplayItem.h"
 #include "platform/graphics/paint/DisplayItemList.h"
 
 namespace blink {
 
 BoxClipper::BoxClipper(const LayoutBox& box, const PaintInfo& paintInfo, const LayoutPoint& accumulatedOffset, ContentsClipBehavior contentsClipBehavior)
     : m_box(box)
     , m_paintInfo(paintInfo)
     , m_clipType(DisplayItem::UninitializedType)
 {
     if (m_paintInfo.phase == PaintPhaseBlockBackground || m_paintInfo.phase == PaintPhaseSelfOutline || m_paintInfo.phase == PaintPhaseMask)
         return;
 
     bool isControlClip = m_box.hasControlClip();
-    bool isOverflowClip = m_box.hasOverflowClip() && !m_box.layer()->isSelfPaintingLayer();
+    bool isOverflowClip = m_box.hasOverflowClip() && (!m_box.layer()->isSelfPaintingLayer() || RuntimeEnabledFeatures::slimmingPaintV2Enabled());

[chrishtr, 2015/09/17 18:07:53]

Why this change?

 
     if (!isControlClip && !isOverflowClip)
         return;
 
     LayoutRect clipRect = isControlClip ? m_box.controlClipRect(accumulatedOffset) : m_box.overflowClipRect(accumulatedOffset);
     FloatRoundedRect clipRoundedRect(0, 0, 0, 0);
     bool hasBorderRadius = m_box.style()->hasBorderRadius();
     if (hasBorderRadius)
         clipRoundedRect = m_box.style()->getRoundedInnerBorderFor(LayoutRect(accumulatedOffset, m_box.size()));
 
-    if (contentsClipBehavior == SkipContentsClipIfPossible) {
+    if (contentsClipBehavior == SkipContentsClipIfPossible && !RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {

[chrishtr, 2015/09/17 18:07:53]

Is this change because we want to preserve clips in phase 2 even if they are
no-op, in order to make overflowClip composite more easily?

         LayoutRect contentsVisualOverflow = m_box.contentsVisualOverflowRect();
         if (contentsVisualOverflow.isEmpty())
             return;
 
         LayoutRect conservativeClipRect = clipRect;
         if (hasBorderRadius)
             conservativeClipRect.intersect(LayoutRect(clipRoundedRect.radiusCenterRect()));
         conservativeClipRect.moveBy(-accumulatedOffset);
         if (m_box.hasLayer())
             conservativeClipRect.move(m_box.scrolledContentOffset());
         if (conservativeClipRect.contains(contentsVisualOverflow))
             return;
     }
 
     ASSERT(m_paintInfo.context->displayItemList());
     if (!m_paintInfo.context->displayItemList()->displayItemConstructionIsDisabled()) {
         m_clipType = m_paintInfo.displayItemTypeForClipping();
         Vector<FloatRoundedRect> roundedRects;
         if (hasBorderRadius)
             roundedRects.append(clipRoundedRect);
         m_paintInfo.context->displayItemList()->createAndAppend<ClipDisplayItem>(m_box, m_clipType, pixelSnappedIntRect(clipRect), roundedRects);
     }
 }
 
 BoxClipper::~BoxClipper()
 {
     if (m_clipType == DisplayItem::UninitializedType)
         return;
 
-    ASSERT(m_box.hasControlClip() || (m_box.hasOverflowClip() && !m_box.layer()->isSelfPaintingLayer()));
+    ASSERT(m_box.hasControlClip() || (m_box.hasOverflowClip() && (!m_box.layer()->isSelfPaintingLayer() || RuntimeEnabledFeatures::slimmingPaintV2Enabled())));
     ASSERT(m_paintInfo.context->displayItemList());
     if (!m_paintInfo.context->displayItemList()->displayItemConstructionIsDisabled()) {
         if (m_paintInfo.context->displayItemList()->lastDisplayItemIsNoopBegin())
             m_paintInfo.context->displayItemList()->removeLastDisplayItem();
         else
             m_paintInfo.context->displayItemList()->createAndAppend<EndClipDisplayItem>(m_box, DisplayItem::clipTypeToEndClipType(m_clipType));
     }
 }
 
 } // namespace blink