[LayoutNG] Update NGPaintFragment.VisualRect() including selection

VisualRect() should cover all visual effects including selections on SPVv175
because SPv175 uses VisualRect() instead of LocalSelectionRect() to invalidate selection.
SPv1 also did that and the future SPv175 will do that when the DisplayItemClient
needs full invalidation.

This patch updates ComputeVisualRectInBacking to add selection rect
to NGPaintFragment.VisualRect() for selection invalidating.
Since NGPaintFragment.VisualRect() didn't consider selection rect,
we missed invalidation.
This patch fixes the problem by updating ComputeVisualRectInBacking to compute
whole visual rect which consists of physical_fragment.VisualRect and
NGPaintFragment::ComputeLocalSelectionRect().

ToT:
https://test-results.appspot.com/data/layout_results/linux_layout_tests_layout_ng/5662/layout-test-results/paint/selection/text-selection-newline-across-blocks-actual.png
This patch:
https://test-results.appspot.com/data/layout_results/linux_layout_tests_layout_ng/5710/layout-test-results/paint/selection/text-selection-newline-across-blocks-actual.png

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2;master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Ie72e3dca922cba0a4c4585cb757156dd543b9bfc
Reviewed-on: https://chromium-review.googlesource.com/1068947Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Yoichi Osato <yoichio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561802}

third_party/blink/renderer/core/paint/paint_invalidator.cc

@@ -255,13 +255,30 @@ LayoutRect PaintInvalidator::ComputeVisualRectInBacking(
       object, local_rect, context);
 }
 
+// We need update |fragment| visual rect considering selection.
+static LayoutRect ComputeLocalVisualRect(const NGPaintFragment& fragment) {
+  const NGPhysicalFragment& physical_fragment = fragment.PhysicalFragment();
+  LayoutRect rect = physical_fragment.VisualRectWithContents().ToLayoutRect();
+  if (!physical_fragment.IsText())
+    return rect;
+  const FrameSelection& frame_selection =
+      fragment.GetLayoutObject()->GetFrame()->Selection();
+  const LayoutSelectionStatus status =
+      frame_selection.ComputeLayoutSelectionStatus(fragment);
+  if (status.start == status.end)
+    return rect;
+  NGPhysicalOffsetRect fragment_rect =
+      fragment.ComputeLocalSelectionRect(status);
+  fragment_rect.offset += fragment.InlineOffsetToContainerBox();
+  rect.Unite(fragment_rect.ToLayoutRect());
+  return rect;
+}
+
 LayoutRect PaintInvalidator::ComputeVisualRectInBacking(
     const NGPaintFragment& fragment,
     const LayoutObject& object,
     const PaintInvalidatorContext& context) {
-  const NGPhysicalFragment& physical_fragment = fragment.PhysicalFragment();
-  LayoutRect local_rect =
-      physical_fragment.VisualRectWithContents().ToLayoutRect();
+  LayoutRect local_rect = ComputeLocalVisualRect(fragment);
   bool disable_flip = true;
   LayoutRect backing_rect =
       MapLocalRectToVisualRectInBacking<LayoutRect, LayoutPoint>(