Update transform paint property's transform-offset on element size 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 1685 matching lines @@
 void LayoutBox::frameRectChanged() {
   if (node() && node()->isElementNode()) {
     Element& element = toElement(*node());
     element.setNeedsResizeObserverUpdate();
   }
   // The frame rect may change because of layout of other objects.
   // Should check this object for paint invalidation.
   if (!needsLayout())
     setMayNeedPaintInvalidation();
 
-  // 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 framerect changes.
-  if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() &&
-      shouldClipOverflow())
-    setNeedsPaintPropertyUpdate();
+  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(...).

[Xianzhu, 2016/12/22 17:28:41]

Just thought of
1. perspective-origin has the same issue.
2. the above condition also covers other percent/calculated values of
transforms, which should be mentioned in the comments.

Can you address these, and perhaps add tests?

+      setNeedsPaintPropertyUpdate();
+    }
+  }
 }
 
 bool LayoutBox::intersectsVisibleViewport() const {
   LayoutRect rect = visualOverflowRect();
   LayoutView* layoutView = view();
   while (!layoutView->frame()->ownerLayoutItem().isNull())
     layoutView =
         LayoutAPIShim::layoutObjectFrom(layoutView->frame()->ownerLayoutItem())
             ->view();
   mapToVisualRectInAncestorSpace(layoutView, rect);
@@ skipping 3947 matching lines @@
     block->adjustChildDebugRect(rect);
 
   return rect;
 }
 
 bool LayoutBox::shouldClipOverflow() const {
   return hasOverflowClip() || styleRef().containsPaint() || hasControlClip();
 }
 
 }  // namespace blink