Allow certain SP recorder classes to defer their "begin" operation.

Source/core/paint/LayerClipRecorder.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/LayerClipRecorder.h"
 
 #include "core/layout/ClipRect.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/IntRect.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/ClipRecorder.h"
 #include "platform/graphics/paint/DisplayItemList.h"
 
 namespace blink {
 
+LayerClipRecorder::LayerClipRecorder(GraphicsContext& graphicsContext, DisplayItem::Type clipType)
+    : m_graphicsContext(graphicsContext)
+    , m_layoutObject(nullptr)
+    , m_clipType(clipType)
+    , m_engaged(false)
+{
+}
+
 LayerClipRecorder::LayerClipRecorder(GraphicsContext& graphicsContext, const LayoutBoxModelObject& layoutObject, DisplayItem::Type clipType, const ClipRect& clipRect,
     const DeprecatedPaintLayerPaintingInfo* localPaintingInfo, const LayoutPoint& fragmentOffset, PaintLayerFlags paintFlags, BorderRadiusClippingRule rule)
-    : m_graphicsContext(graphicsContext)
-    , m_layoutObject(layoutObject)
-    , m_clipType(clipType)
+    : LayerClipRecorder(graphicsContext, clipType)
 {
-    IntRect snappedClipRect = pixelSnappedIntRect(clipRect.rect());
-    OwnPtr<ClipDisplayItem> clipDisplayItem = ClipDisplayItem::create(layoutObject, clipType, snappedClipRect);
-    if (localPaintingInfo && clipRect.hasRadius())
-        collectRoundedRectClips(*layoutObject.layer(), *localPaintingInfo, graphicsContext, fragmentOffset, paintFlags, rule, clipDisplayItem->roundedRectClips());
-    if (!RuntimeEnabledFeatures::slimmingPaintEnabled()) {
-        clipDisplayItem->replay(graphicsContext);
-    } else {
-        ASSERT(m_graphicsContext.displayItemList());
-        if (m_graphicsContext.displayItemList()->displayItemConstructionIsDisabled())
-            return;
-        m_graphicsContext.displayItemList()->add(clipDisplayItem.release());
-    }
+    begin(layoutObject, clipRect, localPaintingInfo, fragmentOffset, paintFlags, rule);
 }
 
 static bool inContainingBlockChain(DeprecatedPaintLayer* startLayer, DeprecatedPaintLayer* endLayer)
 {
     if (startLayer == endLayer)
         return true;
 
     LayoutView* view = startLayer->layoutObject()->view();
     for (LayoutBlock* currentBlock = startLayer->layoutObject()->containingBlock(); currentBlock && currentBlock != view; currentBlock = currentBlock->containingBlock()) {
         if (currentBlock->layer() == endLayer)
@@ skipping 23 matching lines @@
             roundedRectClips.append(layer->layoutObject()->style()->getRoundedInnerBorderFor(LayoutRect(delta, LayoutSize(layer->size()))));
         }
 
         if (layer == localPaintingInfo.rootLayer)
             break;
     }
 }
 
 LayerClipRecorder::~LayerClipRecorder()
 {
+    if (!m_engaged)
+        return;
+
     if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
         ASSERT(m_graphicsContext.displayItemList());
         if (m_graphicsContext.displayItemList()->displayItemConstructionIsDisabled())
             return;
         DisplayItem::Type endType = DisplayItem::clipTypeToEndClipType(m_clipType);
-        OwnPtr<EndClipDisplayItem> endClip = EndClipDisplayItem::create(m_layoutObject, endType);
+        OwnPtr<EndClipDisplayItem> endClip = EndClipDisplayItem::create(*m_layoutObject, endType);
         m_graphicsContext.displayItemList()->add(endClip.release());
     } else {
         m_graphicsContext.restore();
     }
 }
 
+void LayerClipRecorder::begin(const LayoutBoxModelObject& layoutObject, const ClipRect& clipRect, const DeprecatedPaintLayerPaintingInfo* localPaintingInfo, const LayoutPoint& fragmentOffset, PaintLayerFlags paintFlags, BorderRadiusClippingRule rule)
+{
+    ASSERT(!m_engaged);
+    m_engaged = true;
+    m_layoutObject = &layoutObject;
+
+    IntRect snappedClipRect = pixelSnappedIntRect(clipRect.rect());
+    OwnPtr<ClipDisplayItem> clipDisplayItem = ClipDisplayItem::create(*m_layoutObject, m_clipType, snappedClipRect);
+    if (localPaintingInfo && clipRect.hasRadius())
+        collectRoundedRectClips(*m_layoutObject->layer(), *localPaintingInfo, m_graphicsContext, fragmentOffset, paintFlags, rule, clipDisplayItem->roundedRectClips());
+    if (!RuntimeEnabledFeatures::slimmingPaintEnabled()) {
+        clipDisplayItem->replay(m_graphicsContext);
+    } else {
+        ASSERT(m_graphicsContext.displayItemList());
+        if (m_graphicsContext.displayItemList()->displayItemConstructionIsDisabled())
+            return;
+        m_graphicsContext.displayItemList()->add(clipDisplayItem.release());
+    }
+}
+
 } // namespace blink