Absolute positioned child with percent should include containing block padding

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 1731bfdc8fb11f2106df08cf8099ecb01905d4c0..b3b7ca8190e4d48a47442fa5ee67b84ea5b0479b 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -1606,6 +1606,21 @@ LayoutUnit LayoutBox::shrinkLogicalWidthToAvoidFloats(LayoutUnit childMarginStar
     return width;
 }
 
+LayoutUnit LayoutBox::containingBlockLogicalWidthForGetComputedStyle() const
+{
+    if (hasOverrideContainingBlockLogicalWidth())
+        return overrideContainingBlockContentLogicalWidth();
+
+    if (!isPositioned())
+        return containingBlockLogicalWidthForContent();
+
+    LayoutBoxModelObject* cb = toLayoutBoxModelObject(container());

[esprehn, 2016/04/14 18:43:09]

why is container correct vs containingBlock?

[Deokjin Kim, 2016/04/20 13:42:09]

I think this issue is caused by the difference between clientLogicalWidth() and
availableLogicalWidth(). clientLogicalWidth() includes padding, but
availableLogicalWidth() doesn't include padding.

+    LayoutUnit width = containingBlockLogicalWidthForPositioned(cb);
+    if (styleRef().position() != AbsolutePosition)
+        width -= cb->paddingLogicalWidth();
+    return width;
+}
+
 LayoutUnit LayoutBox::containingBlockLogicalHeightForGetComputedStyle() const
 {
     if (hasOverrideContainingBlockLogicalHeight())