Fix gradient background invalidation when HTML size changes

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

+// Copyright 2017 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/ViewPaintInvalidator.h"
+
+#include "core/layout/LayoutView.h"
+#include "core/paint/BoxPaintInvalidator.h"
+#include "platform/geometry/LayoutSize.h"
+
+namespace blink {
+
+PaintInvalidationReason ViewPaintInvalidator::invalidatePaintIfNeeded() {
+  invalidateBackgroundIfNeeded();
+  return BoxPaintInvalidator(m_view, m_context).invalidatePaintIfNeeded();
+}
+
+void ViewPaintInvalidator::invalidateBackgroundIfNeeded() {
+  // Fixed attachment background is handled in LayoutView::layout().
+  // TODO(wangxianzhu): Combine code for fixed-attachment background when we
+  // enable rootLayerScrolling permanently.
+  if (m_view.styleRef().hasEntirelyFixedBackground())
+    return;
+
+  // LayoutView's non-fixed-attachment background is positioned in the
+  // document element.
+  // See https://drafts.csswg.org/css-backgrounds-3/#root-background.
+  Element* documentElement = m_view.document().documentElement();
+  if (!documentElement)
+    return;
+  const LayoutObject* backgroundObject = documentElement->layoutObject();
+  if (!backgroundObject || !backgroundObject->isBox())
+    return;
+
+  const LayoutBox& backgroundBox = toLayoutBox(*backgroundObject);
+  LayoutSize oldSize = BoxPaintInvalidator::previousBorderBoxSize(
+      backgroundBox, backgroundBox.visualRect().size());
+  LayoutSize newSize = backgroundBox.size();
+  const auto& backgroundLayers = m_view.styleRef().backgroundLayers();
+  if ((oldSize.width() != newSize.width() &&
+       LayoutBox::mustInvalidateFillLayersPaintOnWidthChange(
+           backgroundLayers)) ||
+      (oldSize.height() != newSize.height() &&
+       LayoutBox::mustInvalidateFillLayersPaintOnHeightChange(
+           backgroundLayers))) {
+    m_view.getMutableForPainting().setShouldDoFullPaintInvalidation(
+        PaintInvalidationViewBackground);
+  }
+}
+
+}  // namespace blink