LayoutView's paint layer should clip to the full viewport size.

third_party/WebKit/Source/web/tests/VisualViewportTest.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/frame/VisualViewport.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/BrowserControls.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
@@ skipping 2267 matching lines @@
   ASSERT_TRUE(invalidationTracking);
 
   const auto* rasterInvalidations =
       &invalidationTracking->trackedRasterInvalidations;
 
   bool rootLayerScrolling = GetParam();
 
   // Without root-layer-scrolling, the LayoutView is the size of the document
   // content so invalidating it for background-attachment: fixed
   // overinvalidates as we should only need to invalidate the viewport size.
-  int expectedHeight = rootLayerScrolling ? 430 : 1000;
+  // With root-layer-scrolling, we should invalidate the entire viewport height.
+  int expectedHeight = rootLayerScrolling ? pageHeight : 1000;
 
   // The entire viewport should have been invalidated.
   EXPECT_EQ(1u, rasterInvalidations->size());
   EXPECT_EQ(IntRect(0, 0, 640, expectedHeight), (*rasterInvalidations)[0].rect);
   document->view()->setTracksPaintInvalidations(false);
 
   invalidationTracking = document->layoutView()
                              ->layer()
                              ->graphicsLayerBacking()
                              ->getRasterInvalidationTracking();
@@ skipping 98 matching lines @@
   if (rootLayerScrolling)
     EXPECT_TRUE(invalidationTracking);
   else
     EXPECT_FALSE(invalidationTracking);
 
   document->view()->setTracksPaintInvalidations(false);
   RuntimeEnabledFeatures::setInertTopControlsEnabled(originalInertTopControls);
 }
 
 }  // namespace