Paint solid color backgrounds which are equivalent to locally attached into scrolling contents layer

third_party/WebKit/Source/core/style/ComputedStyle.cpp

Index: third_party/WebKit/Source/core/style/ComputedStyle.cpp
diff --git a/third_party/WebKit/Source/core/style/ComputedStyle.cpp b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
index 227d0f12e1d8f04b964c54243687efaddc5c82c5..a8621108df516216ef516f5ee7d0c46c66080ae3 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.cpp
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
@@ -1268,12 +1268,30 @@ bool ComputedStyle::hasEntirelyLocalBackground() const
     for (; layer; layer = layer->next()) {
         if (layer->attachment() == LocalBackgroundAttachment)
             continue;
-        // Solid color layers with a background clip of the padding box can be treated
+        // Solid color layers with an effective background clip of the padding box can be treated
         // as local.
-        // TODO(flackr): We can handle other fill boxes with solid colors as long as they
-        // are essentially the same (i.e. PaddingFillBox == ContentFillBox when padding = 0).
-        if (!layer->image() && !layer->next() && layer->clip() == PaddingFillBox)
-            continue;
+        if (!layer->image() && !layer->next()) {
+            EFillBox clip = layer->clip();
+            if (clip == PaddingFillBox)
+                continue;
+            // A border box can be treated as a padding box if the border is opaque or there is
+            // no border.
+            if (clip == BorderFillBox
+                && (borderTopWidth() == 0 || !visitedDependentColor(CSSPropertyBorderTopColor).hasAlpha())
+                && (borderLeftWidth() == 0 || !visitedDependentColor(CSSPropertyBorderLeftColor).hasAlpha())
+                && (borderRightWidth() == 0 || !visitedDependentColor(CSSPropertyBorderRightColor).hasAlpha())
+                && (borderBottomWidth() == 0 || !visitedDependentColor(CSSPropertyBorderBottomColor).hasAlpha())) {
+                continue;
+            }
+            // A content fill box can be treated as a padding fill box if there is no padding.
+            if (clip == ContentFillBox
+                && paddingTop().isZero()
+                && paddingLeft().isZero()
+                && paddingRight().isZero()
+                && paddingBottom().isZero()) {
+                continue;
+            }
+        }
         return false;
     }
     return true;