Clear scroll anchor on all parent scrollers from ScrollAnchor::clear

third_party/WebKit/Source/core/layout/ScrollAnchorTest.cpp

 // Copyright 2015 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/ScrollAnchor.h"
 
 #include "core/dom/ClientRect.h"
 #include "core/frame/VisualViewport.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutTestHelper.h"
@@ skipping 223 matching lines @@
 
   document().getElementById("scroller")->setScrollTop(1600);
 
   setHeight(document().getElementById("changer"), 0);
 
   EXPECT_EQ(100, scroller->scrollOffsetInt().height());
   EXPECT_EQ(document().getElementById("anchor")->layoutObject(),
             scrollAnchor(scroller).anchorObject());
 }
 
+// Test that a non-anchoring scroll on scroller clears scroll anchors for all
+// parent scrollers.
+TEST_F(ScrollAnchorTest, ClearScrollAnchorsOnAncestors) {
+  setBodyInnerHTML(
+      "<style>"
+      "    body { height: 1000px } div { height: 200px }"
+      "    #scroller { height: 100px; width: 200px; overflow: scroll; }"
+      "</style>"
+      "<div id='changer'>abc</div>"
+      "<div id='anchor'>def</div>"
+      "<div id='scroller'><div></div></div>");
+
+  ScrollableArea* viewport = layoutViewport();
+
+  scrollLayoutViewport(ScrollOffset(0, 250));
+  setHeight(document().getElementById("changer"), 300);
+
+  EXPECT_EQ(350, viewport->scrollOffsetInt().height());
+  EXPECT_EQ(document().getElementById("anchor")->layoutObject(),
+            scrollAnchor(viewport).anchorObject());
+
+  // Scrolling the nested scroller should clear the anchor on the main frame.
+  ScrollableArea* scroller =
+      scrollerForElement(document().getElementById("scroller"));
+  scroller->scrollBy(ScrollOffset(0, 100), UserScroll);
+  EXPECT_EQ(nullptr, scrollAnchor(viewport).anchorObject());
+}
+
 TEST_F(ScrollAnchorTest, FractionalOffsetsAreRoundedBeforeComparing) {
   setBodyInnerHTML(
       "<style> body { height: 1000px } </style>"
       "<div id='block1' style='height: 50.4px'>abc</div>"
       "<div id='block2' style='height: 100px'>def</div>");
 
   ScrollableArea* viewport = layoutViewport();
   scrollLayoutViewport(ScrollOffset(0, 100));
 
   document().getElementById("block1")->setAttribute(HTMLNames::styleAttr,
@@ skipping 725 matching lines @@
 
   scrollLayoutViewport(ScrollOffset(-50, 0));
 
   a->setAttribute(HTMLNames::styleAttr, "width: 200px");
   b->setAttribute(HTMLNames::styleAttr, "height: 150px");
   update();
   EXPECT_EQ(ScrollOffset(-100, 150), viewport->scrollOffset());
   EXPECT_EQ(c->layoutObject(), scrollAnchor(viewport).anchorObject());
 }
 }