Paint local background colors onto foreground layer.

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 246ccabb2e3a81e661dac034b68b9c451e15b57f..86d0ecd01d221d8fba1df72b4a00b10b0c0a4694 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -1789,13 +1789,12 @@ void LayoutBox::mapAncestorToLocal(const LayoutBoxModelObject* ancestor, Transfo
 
     bool isFixedPos = style()->position() == FixedPosition;
 
-    if (style()->canContainFixedPositionObjects() && !isFixedPos) {
-        // If this box has a transform or contains paint, it acts as a fixed position container for fixed descendants,
-        // and may itself also be fixed position. So propagate 'fixed' up only if this box is fixed position.
+    // If this box has a transform or contains paint, it acts as a fixed position container for fixed descendants,
+    // and may itself also be fixed position. So propagate 'fixed' up only if this box is fixed position.
+    if (style()->canContainFixedPositionObjects() && !isFixedPos)

[chrishtr, 2016/07/29 21:04:34]

Spurious changes here?

[flackr, 2016/08/02 16:58:14]

schenney suggested I move the comment in ... while I was touching LayoutBox.cpp
to be consistent with the comment in mapLocalToAncestor. Although I guess
currently I'm not otherwise touching LayoutBox.cpp, removed.

         mode &= ~IsFixed;
-    } else if (isFixedPos) {
+    else if (isFixedPos)
         mode |= IsFixed;
-    }
 
     LayoutBoxModelObject::mapAncestorToLocal(ancestor, transformState, mode);
 }