Paint local attachment backgrounds into composited scrolling contents layer

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/compositing/CompositedLayerMapping.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/api/LayoutViewItem.h"
@@ skipping 621 matching lines @@
     EXPECT_FALSE(mapping->foregroundLayer());
 }
 
 TEST_F(CompositedLayerMappingTest, ShouldPaintBackgroundOntoScrollingContentsLayer)
 {
     document().frame()->settings()->setPreferCompositingToLCDTextEnabled(true);
     setBodyInnerHTML(
         "<style>.scroller { overflow: scroll; will-change: transform; width: 300px; height: 300px;} .spacer { height: 1000px; }</style>"
         "<div id='scroller1' class='scroller' style='background: white local;'>"
         "    <div id='negative-composited-child' style='background-color: red; width: 1px; height: 1px; position: absolute; backface-visibility: hidden; z-index: -1'></div>"
-        "    <div class='spacer'></div>"
         "</div>"
-        "<div id='scroller2' class='scroller' style='background: white content-box; padding: 10px;'>"
-        "    <div class='spacer'></div>"
-        "</div>"
-        "<div id='scroller3' class='scroller' style='background: white local content-box; padding: 10px;'>"
-        "    <div class='spacer'></div>"
-        "</div>"
+        "<div id='scroller2' class='scroller' style='background: white content-box; padding: 10px;'></div>"
+        "<div id='scroller3' class='scroller' style='background: white local content-box; padding: 10px;'></div>"
+        "<div id='scroller4' class='scroller' style='background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUg), white local;'></div>"
+        "<div id='scroller5' class='scroller' style='background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUg) local, white local;'></div>"
+        "<div id='scroller6' class='scroller' style='background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUg) local, white padding-box; padding: 10px;'></div>"
+        "<div id='scroller7' class='scroller' style='background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUg) local, white content-box; padding: 10px;'></div>"
         );
 
     // First scroller cannot paint background into scrolling contents layer because it has a negative z-index child.
     EXPECT_FALSE(shouldPaintBackgroundOntoScrollingContentsLayer("scroller1"));
 
     // Second scroller cannot paint background into scrolling contents layer because it has a content-box clip without local attachment.
     EXPECT_FALSE(shouldPaintBackgroundOntoScrollingContentsLayer("scroller2"));
 
     // Third scroller can paint background into scrolling contents layer.
     EXPECT_TRUE(shouldPaintBackgroundOntoScrollingContentsLayer("scroller3"));
+
+    // Fourth scroller cannot paint background into scrolling contents layer because the background image is not locally attached.

[chrishtr, 2016/08/12 17:03:00]

You said "cannot" but have EXPECT_TRUE below.

[flackr, 2016/08/16 17:52:51]

Oops, fixed.

+    EXPECT_TRUE(shouldPaintBackgroundOntoScrollingContentsLayer("scroller4"));
+
+    // Fifth scroller can paint background into scrolling contents layer because both the image and color are locally attached.
+    EXPECT_TRUE(shouldPaintBackgroundOntoScrollingContentsLayer("scroller5"));
+
+    // Sixth scroller can paint background into scrolling contents layer because the image is locally attached and even though
+    // the color is not, it is filled to the padding box so it will be drawn the same as a locally attached background.
+    EXPECT_TRUE(shouldPaintBackgroundOntoScrollingContentsLayer("scroller6"));
+
+    // Seventh scroller cannot paint background into scrolling contents layer because the color is filled to the content
+    // box and we have padding so it is not equivalent to a locally attached background.
+    EXPECT_FALSE(shouldPaintBackgroundOntoScrollingContentsLayer("scroller7"));
 }
 
 } // namespace blink