Skip paint offset caching when DisplayItemList is skipping cache

third_party/WebKit/Source/core/paint/BlockPainter.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/BlockPainter.h"
 
 #include "core/editing/DragCaretController.h"
 #include "core/editing/FrameSelection.h"
 #include "core/frame/Settings.h"
@@ skipping 125 matching lines @@
         layoutObject.paint(info, childPoint);
         info.phase = PaintPhaseForeground;
         layoutObject.paint(info, childPoint);
         info.phase = PaintPhaseOutline;
         layoutObject.paint(info, childPoint);
     }
 }
 
 void BlockPainter::paintObject(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
-    if (RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled() && m_layoutBlock.childrenInline()) {
+    if (RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled() && m_layoutBlock.childrenInline() && !paintInfo.context->displayItemList()->skippingCache()) {

[pdr., 2015/10/06 03:10:25]

WDYT about renaming skippingCache to skippingCacheAndPaintOffsetChecks()? I
think it's likely we will forget that skipping the cache also skips the paint
offset code.

We could then update the setPreviousPaintOffset calls to
ASSERT(!skippingCacheAndPaintOffsetChecks());

[Xianzhu, 2015/10/06 16:35:23]

I think paint offset cache is also a cache that skip-cache should skip :) 
I'd like LayoutObject no to know such details of DisplayItemList. The current
DisplayItemList::invalidatePaintOffset() assertions are enough to discover such
issues.

         if (m_layoutBlock.paintOffsetChanged(paintOffset)) {
             LineBoxListPainter(m_layoutBlock.lineBoxes()).invalidateLineBoxPaintOffsets(paintInfo);
             paintInfo.context->displayItemList()->invalidatePaintOffset(m_layoutBlock);
         }
         // Set previousPaintOffset here in case that m_layoutBlock paints nothing and no
         // LayoutObjectDrawingRecorder updates its previousPaintOffset.
         // TODO(wangxianzhu): Integrate paint offset checking into new paint invalidation.
         m_layoutBlock.setPreviousPaintOffset(paintOffset);
     }
 
@@ skipping 102 matching lines @@
 
         // We don't paint our own background, but we do let the kids paint their backgrounds.
         PaintInfo paintInfoForChild(paintInfo);
         paintInfoForChild.phase = newPhase;
         paintInfoForChild.updatePaintingRootForChildren(&m_layoutBlock);
         m_layoutBlock.paintChildren(paintInfoForChild, paintOffset);
     }
 }
 
 } // namespace blink