Fix ScrollAnchor descent into absolute-positioned containers.

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 529 matching lines @@
   scrollerElement->setAttribute(HTMLNames::styleAttr, "position: relative");
   update();
   scroller->scrollBy(ScrollOffset(0, 25), UserScroll);
   setHeight(document().getElementById("a"), 125);
 
   // When the scroller is position:relative, the anchor may be
   // position:absolute.
   EXPECT_EQ(absPos->layoutObject(), scrollAnchor(scroller).anchorObject());
 }
 
+TEST_P(ScrollAnchorTest, DescendsIntoAbsPosWithOffscreenStaticParent) {
+  setBodyInnerHTML(
+      "<style>"
+      "  body, html { height: 0; }"
+      "  #abs {"
+      "    position: absolute;"
+      "    left: 50px;"
+      "    top: 50px;"
+      "    height: 1200px;"
+      "    padding: 50px;"
+      "    border: 5px solid gray;"
+      "  }"
+      "  #anchor {"
+      "    background-color: #afa;"
+      "    width: 100px;"
+      "    height: 100px;"
+      "  }"
+      "</style>"
+      "<div id='abs'>"
+      "  <div id='changer'></div>"
+      "  <div id='anchor'></div>"
+      "</div>");
+
+  scrollLayoutViewport(ScrollOffset(0, 120));
+  setHeight(document().getElementById("changer"), 100);
+  EXPECT_EQ(220, layoutViewport()->scrollOffsetInt().height());
+}
+
 // Test that we descend into zero-height containers that have overflowing
 // content.
 TEST_P(ScrollAnchorTest, DescendsIntoContainerWithOverflow) {
   setBodyInnerHTML(
       "<style>"
       "    body { height: 1000; }"
       "    #outer { width: 300px; }"
       "    #zeroheight { height: 0px; }"
       "    #changer { height: 100px; background-color: red; }"
       "    #bottom { margin-top: 600px; }"
@@ skipping 579 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->getScrollOffset());
   EXPECT_EQ(c->layoutObject(), scrollAnchor(viewport).anchorObject());
 }
 }