Fix gradient background invalidation when HTML size changes

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

Index: third_party/WebKit/Source/core/paint/ViewPaintInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/paint/ViewPaintInvalidator.cpp b/third_party/WebKit/Source/core/paint/ViewPaintInvalidator.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..4a68e21520bdbcadf9cfc25d94a887d64278dc1c
--- /dev/null
+++ b/third_party/WebKit/Source/core/paint/ViewPaintInvalidator.cpp
@@ -0,0 +1,41 @@
+// 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() {
+  if (!m_view.styleRef().hasEntirelyFixedBackground()) {
+    // LayoutView's non-fixed-attachment background is positioned in the
+    // document element.
+    if (Element* documentElement = m_view.document().documentElement()) {
+      const LayoutObject* backgroundObject = documentElement->layoutObject();
+      if (backgroundObject && backgroundObject->isBox()) {
+        const LayoutBox& backgroundBox = toLayoutBox(*backgroundObject);
+        LayoutSize oldSize =
+            BoxPaintInvalidator::previousBorderBoxSize(backgroundBox);
+        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);
+        }
+      }
+    }
+  }
+
+  return BoxPaintInvalidator(m_view, m_context).invalidatePaintIfNeeded();
+}
+
+}  // namespace blink