Take CSS Clip and contain: paint into account when computing visual rects.

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

Index: third_party/WebKit/Source/core/layout/LayoutBox.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.h b/third_party/WebKit/Source/core/layout/LayoutBox.h
index 4c619bb8fd567091e1704f2ccfa12705ce84eb76..9267cd0132b4eb0d6efe00c56463c618e8a33b0d 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.h
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.h
@@ -803,6 +803,9 @@ public:
     virtual bool hasControlClip() const { return false; }
     virtual LayoutRect controlClipRect(const LayoutPoint&) const { return LayoutRect(); }
 
+    // Returns the combination of overflow clip, contain: paint clip and CSS clip for this object, in local space.

[Xianzhu, 2016/08/12 17:07:57]

What about control clip?

[chrishtr, 2016/08/12 17:56:24]

Control clip on only affects LayoutButton, LayoutMenuList and
LayoutTextControlSingleLine. I tried to modify
PaintPropertyTreeBuilderTest.ControlClip to check visual rects for hidden layout
children of the button, but the LayoutBlockFlow which contains the LayoutText of
the button already has a size that is smaller than the control clip, and the
LayoutText doesn't
have an ObjectPaintProperties object at present (optimized out), which makes it
more boilerplate to test.

I don't think it's worth it to add this. WDYT?

[Xianzhu, 2016/08/12 18:45:46]

SGTM.

+    LayoutRect clippingRect() const;
+
     virtual void paintBoxDecorationBackground(const PaintInfo&, const LayoutPoint&) const;
     virtual void paintMask(const PaintInfo&, const LayoutPoint&) const;
     void imageChanged(WrappedImagePtr, const IntRect* = nullptr) override;