Do not promote position sticky or fixed elements unless they move with scroll.

third_party/WebKit/Source/core/paint/PaintLayerTest.cpp

 // Copyright 2016 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/paint/PaintLayer.h"
 
 #include "core/html/HTMLIFrameElement.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutView.h"
@@ skipping 111 matching lines @@
   EXPECT_EQ(
       LayoutRect(90, 40, 110, 243),
       layer->paintingExtent(document().layoutView()->layer(), LayoutSize(), 0));
 }
 
 TEST_P(PaintLayerTest, ScrollsWithViewportRelativePosition) {
   setBodyInnerHTML("<div id='target' style='position: relative'></div>");
 
   PaintLayer* layer =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
-  EXPECT_FALSE(layer->sticksToViewport());
+  EXPECT_FALSE(layer->fixedToViewport());
 }
 
 TEST_P(PaintLayerTest, ScrollsWithViewportFixedPosition) {
   setBodyInnerHTML("<div id='target' style='position: fixed'></div>");
 
   PaintLayer* layer =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
-  EXPECT_TRUE(layer->sticksToViewport());
+  EXPECT_TRUE(layer->fixedToViewport());
 }
 
 TEST_P(PaintLayerTest, ScrollsWithViewportFixedPositionInsideTransform) {
   // We don't intend to launch SPv2 without root layer scrolling, so skip this
   // test in that configuration because it's broken.
   if (RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&
       !RuntimeEnabledFeatures::rootLayerScrollingEnabled())
     return;
   setBodyInnerHTML(
       "<div style='transform: translateZ(0)'>"
       "  <div id='target' style='position: fixed'></div>"
       "</div>"
       "<div style='width: 10px; height: 1000px'></div>");
   PaintLayer* layer =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
-  EXPECT_FALSE(layer->sticksToViewport());
+  EXPECT_FALSE(layer->fixedToViewport());
 }
 
 TEST_P(PaintLayerTest,
        ScrollsWithViewportFixedPositionInsideTransformNoScroll) {
   setBodyInnerHTML(
       "<div style='transform: translateZ(0)'>"
       "  <div id='target' style='position: fixed'></div>"
       "</div>");
   PaintLayer* layer =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
 
   // In SPv2 mode, we correctly determine that the frame doesn't scroll at all,
   // and so return true.
   if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
-    EXPECT_TRUE(layer->sticksToViewport());
+    EXPECT_TRUE(layer->fixedToViewport());
   else
-    EXPECT_FALSE(layer->sticksToViewport());
+    EXPECT_FALSE(layer->fixedToViewport());
 }
 
-TEST_P(PaintLayerTest, ScrollsWithViewportStickyPosition) {
+TEST_P(PaintLayerTest, SticksToScrollerStickyPosition) {
+  setBodyInnerHTML(
+      "<div style='transform: translateZ(0)'>"
+      "  <div id='target' style='position: sticky; top: 0;'></div>"
+      "</div>"
+      "<div style='width: 10px; height: 1000px'></div>");
+
+  PaintLayer* layer =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
+  EXPECT_TRUE(layer->sticksToScroller());
+}
+
+TEST_P(PaintLayerTest, SticksToScrollerNoAnchor) {
   setBodyInnerHTML(
       "<div style='transform: translateZ(0)'>"
       "  <div id='target' style='position: sticky'></div>"
       "</div>"
       "<div style='width: 10px; height: 1000px'></div>");
 
   PaintLayer* layer =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
-  EXPECT_TRUE(layer->sticksToViewport());
+  EXPECT_FALSE(layer->sticksToScroller());
 }
 
-TEST_P(PaintLayerTest, ScrollsWithViewportStickyPositionNoScroll) {
+TEST_P(PaintLayerTest, SticksToScrollerStickyPositionNoScroll) {
   setBodyInnerHTML(
       "<div style='transform: translateZ(0)'>"
-      "  <div id='target' style='position: sticky'></div>"
+      "  <div id='target' style='position: sticky; top: 0;'></div>"
       "</div>");
 
   PaintLayer* layer =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
-  EXPECT_TRUE(layer->sticksToViewport());
+  EXPECT_TRUE(layer->sticksToScroller());
 }
 
-TEST_P(PaintLayerTest, ScrollsWithViewportStickyPositionInsideScroller) {
+TEST_P(PaintLayerTest, SticksToScrollerStickyPositionInsideScroller) {
   setBodyInnerHTML(
       "<div style='overflow:scroll; width: 100px; height: 100px;'>"
-      "  <div id='target' style='position: sticky'></div>"
+      "  <div id='target' style='position: sticky; top: 0;'></div>"
       "  <div style='width: 50px; height: 1000px;'></div>"
       "</div>");
 
   PaintLayer* layer =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
-  EXPECT_FALSE(layer->sticksToViewport());
+  EXPECT_TRUE(layer->sticksToScroller());
 }
 
 TEST_P(PaintLayerTest, CompositedScrollingNoNeedsRepaint) {
   if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
     return;
 
   enableCompositing();
   setBodyInnerHTML(
       "<div id='scroll' style='width: 100px; height: 100px; overflow: scroll;"
       "    will-change: transform'>"
@@ skipping 518 matching lines @@
   EXPECT_EQ(LayoutPoint(-150, 50), spanner->location());
   EXPECT_EQ(LayoutPoint(100, 100), extraLayer->location());
   // -60 = 2nd-column-x(40) - scroll-offset-x(200) + x-location(100)
   // 20 = y-location(100) - column-height(80)
   EXPECT_EQ(LayoutPoint(-60, 20),
             extraLayer->visualOffsetFromAncestor(columns));
   EXPECT_EQ(LayoutPoint(-150, 50), spanner->visualOffsetFromAncestor(columns));
 }
 
 }  // namespace blink