Update perspective paint properties on perspective-origin changes

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1691 matching lines @@
   // Should check this object for paint invalidation.
   if (!needsLayout())
     setMayNeedPaintInvalidation();
 
   if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
     if (shouldClipOverflow()) {
       // The overflow clip paint property depends on the border box rect through
       // overflowClipRect(). The border box rect's size equals the frame rect's
       // size so we trigger a paint property update when the frame rect changes.
       setNeedsPaintPropertyUpdate();
-    } else if (styleRef().hasTransform()) {
-      // The transform paint property's origin depends on the frame rect because
-      // transform-origin can be sized with lengths relative to the frame rect.
-      // See: PaintPropertyTreeBuilder::updateTransform(...).
+    } else if (styleRef().hasTransform() || styleRef().hasPerspective()) {
+      // Both transform-origin and perspective-origin can change if they use
+      // relative lengths and the frame rect changes.
+      // See: PaintPropertyTreeBuilder's updateTransform and updatePerspective.
+      // TODO(pdr): We only need to update properties if the origin is specified
+      // with relative lengths (e.g., percentage).

[Xianzhu, 2016/12/22 21:55:15]

Nit: Other transform components can also be relative lengths, e.g.
translateX(10%), which is also covered by this condition. Please update comments
to mention this.

       setNeedsPaintPropertyUpdate();
     }
   }
 }
 
 bool LayoutBox::intersectsVisibleViewport() const {
   LayoutRect rect = visualOverflowRect();
   LayoutView* layoutView = view();
   while (!layoutView->frame()->ownerLayoutItem().isNull())
     layoutView =
@@ skipping 3950 matching lines @@
     block->adjustChildDebugRect(rect);
 
   return rect;
 }
 
 bool LayoutBox::shouldClipOverflow() const {
   return hasOverflowClip() || styleRef().containsPaint() || hasControlClip();
 }
 
 }  // namespace blink