Add a hack to set shouldPaint to true for force-composited iframes.

third_party/WebKit/Source/core/layout/FloatingObjects.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "core/layout/FloatingObjects.h"
 
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutView.h"
 #include "core/layout/shapes/ShapeOutsideInfo.h"
+#include "core/paint/PaintLayer.h"
 
 #include <algorithm>
 
 using namespace WTF;
 
 namespace blink {
 
 struct SameSizeAsFloatingObject {
     void* pointers[2];
     LayoutRect rect;
@@ skipping 19 matching lines @@
         m_type = FloatLeft;
     else if (type == RightFloat)
         m_type = FloatRight;
 }
 
 FloatingObject::FloatingObject(LayoutBox* layoutObject, Type type, const LayoutRect& frameRect, bool shouldPaint, bool isDescendant, bool isLowestNonOverhangingFloatInChild)
     : m_layoutObject(layoutObject)
     , m_originatingLine(nullptr)
     , m_frameRect(frameRect)
     , m_type(type)
-    , m_shouldPaint(shouldPaint)
     , m_isDescendant(isDescendant)
     , m_isPlaced(true)
     , m_isLowestNonOverhangingFloatInChild(isLowestNonOverhangingFloatInChild)
 #if ENABLE(ASSERT)
     , m_isInPlacedTree(false)
 #endif
 {
+    m_shouldPaint = shouldPaint || shouldPaintForCompositedLayoutPart();
+}
+
+bool FloatingObject::shouldPaintForCompositedLayoutPart()
+{
+    // HACK: only non-self-painting floats should paint. However, due to the fundamental compositing bug, some LayoutPart objects
+    // may become self-painting due to being composited. This leads to a chicken-egg issue because layout may not depend on compositing.
+    // If this is the case, set shouldPaint() to true even if the layer is technically self-painting. This lets the float which contains
+    // a LayoutPart start painting as soon as it stops being composited, without having to re-layout the float.
+    // This hack can be removed after SPv2.
+    return m_layoutObject->layer() && m_layoutObject->layer()->isSelfPaintingOnlyBecauseIsCompositedPart();
 }
 
 PassOwnPtr<FloatingObject> FloatingObject::create(LayoutBox* layoutObject)
 {
     OwnPtr<FloatingObject> newObj = adoptPtr(new FloatingObject(layoutObject));
-    newObj->setShouldPaint(!layoutObject->hasSelfPaintingLayer()); // If a layer exists, the float will paint itself. Otherwise someone else will.
+
+    // If a layer exists, the float will paint itself. Otherwise someone else will.
+    newObj->setShouldPaint(!layoutObject->hasSelfPaintingLayer()  || newObj->shouldPaintForCompositedLayoutPart());

[Xianzhu, 2016/05/26 18:29:54]

Nit: Remove extra space before '||'.

[chrishtr, 2016/05/26 18:49:29]

Done.

+
     newObj->setIsDescendant(true);
 
     return newObj;
 }
 
+bool FloatingObject::shouldPaint() const
+{
+    return m_shouldPaint && !m_layoutObject->hasSelfPaintingLayer();
+}
+
 PassOwnPtr<FloatingObject> FloatingObject::copyToNewContainer(LayoutSize offset, bool shouldPaint, bool isDescendant) const
 {
     return adoptPtr(new FloatingObject(layoutObject(), getType(), LayoutRect(frameRect().location() - offset, frameRect().size()), shouldPaint, isDescendant, isLowestNonOverhangingFloatInChild()));
 }
 
 PassOwnPtr<FloatingObject> FloatingObject::unsafeClone() const
 {
     OwnPtr<FloatingObject> cloneObject = adoptPtr(new FloatingObject(layoutObject(), getType(), m_frameRect, m_shouldPaint, m_isDescendant, false));
     cloneObject->m_isPlaced = m_isPlaced;
     return cloneObject;
@@ skipping 520 matching lines @@
 }
 
 String ValueToString<FloatingObject*>::toString(const FloatingObject* floatingObject)
 {
     return String::format("%p (%gx%g %gx%g)", floatingObject, floatingObject->frameRect().x().toFloat(), floatingObject->frameRect().y().toFloat(), floatingObject->frameRect().maxX().toFloat(), floatingObject->frameRect().maxY().toFloat());
 }
 #endif
 
 
 } // namespace blink