Invalidate paint properties on paint offset changes

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

Index: third_party/WebKit/Source/core/layout/LayoutBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.cpp b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
index fc48cab3e05c766569f25454af712a7460b27e11..9cc848b652cf494cfe192ad08cf18fd74c5ba87b 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -325,6 +325,17 @@ void LayoutBox::styleDidChange(StyleDifference diff,
     updateScrollSnapMappingAfterStyleChange(&newStyle, oldStyle);
   }
 
+  if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
+    // The overflow clip paint property depends on border sizes through
+    // overflowClipRect(), so we trigger a property update if any border is or
+    // was present. This check could be more precise (checking the actual
+    // border values) if performance is an issue.
+    if (hasOverflowClip() || styleRef().containsPaint() || hasControlClip()) {
+      if (newStyle.hasBorder() || (oldStyle && oldStyle->hasBorder()))

[Xianzhu, 2016/12/05 16:55:53]

How does it work if overflow clip changed without a border?

+        setNeedsPaintPropertyUpdate();
+    }
+  }
+
   // Non-atomic inlines should be LayoutInline or LayoutText, not LayoutBox.
   DCHECK(!isInline() || isAtomicInlineLevel());
 }
@@ -1692,6 +1703,13 @@ void LayoutBox::frameRectChanged() {
   // Should check this object for paint invalidation.
   if (!needsLayout())
     setMayNeedPaintInvalidation();
+
+  if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
+    // The overflow clip paint property depends on the border box rect through
+    // overflowClipRect, which in turn depends on the frame rect.
+    if (hasOverflowClip() || styleRef().containsPaint() || hasControlClip())
+      setNeedsPaintPropertyUpdate();
+  }
 }
 
 bool LayoutBox::intersectsVisibleViewport() const {