Create scroll properties for main thread scrolling even w/o scrolling

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilderTest.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/html/HTMLIFrameElement.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutTreeAsText.h"
 #include "core/layout/api/LayoutViewItem.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintPropertyTreePrinter.h"
@@ skipping 2678 matching lines @@
   EXPECT_TRUE(overflowA->layoutObject()
                   ->paintProperties()
                   ->scroll()
                   ->hasBackgroundAttachmentFixedDescendants());
   EXPECT_FALSE(overflowB->layoutObject()
                    ->paintProperties()
                    ->scroll()
                    ->hasBackgroundAttachmentFixedDescendants());
 }
 
+TEST_P(PaintPropertyTreeBuilderTest, MainThreadScrollReasonsWithoutScrolling) {
+  setBodyInnerHTML(
+      "<style>"
+      "  #overflow {"
+      "    overflow: scroll;"
+      "    width: 100px;"
+      "    height: 100px;"
+      "  }"
+      "  .backgroundAttachmentFixed {"
+      "    background-image: url('foo');"
+      "    background-attachment: fixed;"
+      "    width: 10px;"
+      "    height: 10px;"
+      "  }"
+      "  .forceScroll {"
+      "    height: 4000px;"
+      "  }"
+      "</style>"
+      "<div id='overflow'>"
+      "  <div class='backgroundAttachmentFixed'></div>"
+      "</div>"
+      "<div class='forceScroll'></div>");
+  Element* overflow = document().getElementById("overflow");
+  EXPECT_TRUE(frameScroll()->hasBackgroundAttachmentFixedDescendants());
+  EXPECT_TRUE(overflow->layoutObject()
+                  ->paintProperties()
+                  ->scroll()
+                  ->hasBackgroundAttachmentFixedDescendants());
+}
+
 TEST_P(PaintPropertyTreeBuilderTest,
        BackgroundAttachmentFixedMainThreadScrollReasonsWithFixedScroller) {
   setBodyInnerHTML(
       "<style>"
       "  #overflowA {"
       "    position: absolute;"
       "    overflow: scroll;"
       "    width: 20px;"
       "    height: 20px;"
       "  }"
@@ skipping 314 matching lines @@
   EXPECT_FALSE(document().layoutView()->descendantNeedsPaintPropertyUpdate());
   EXPECT_FALSE(transform->needsPaintPropertyUpdate());
   EXPECT_FALSE(transform->descendantNeedsPaintPropertyUpdate());
   EXPECT_FALSE(iframeLayoutView->needsPaintPropertyUpdate());
   EXPECT_FALSE(iframeLayoutView->descendantNeedsPaintPropertyUpdate());
   EXPECT_FALSE(iframeTransform->needsPaintPropertyUpdate());
   EXPECT_FALSE(iframeTransform->descendantNeedsPaintPropertyUpdate());
 }
 
 }  // namespace blink