[LayoutNG] Implement LayoutInline::LinesVisualOverflowBoundingBox

This patch supports LayoutInline::LinesVisualOverflowBoundingBox()
when LayoutNGPaintFragments is enabled.

Layer painting use this function to determine dirty regions.

This is a split of CL:803875 to measure the fix impacts. Estimated
to fix 385 tests in LayoutNGPaintFragments.

Bug: 714962
Change-Id: I2822528a56d116037fd507dc2c086cdb27c50b2e
Reviewed-on: https://chromium-review.googlesource.com/807972
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: yosin (OOO Dec 11 to Jan 8) <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521660}

third_party/WebKit/Source/core/layout/LayoutInline.cpp

@@ -1113,6 +1113,19 @@ LayoutRect LayoutInline::CulledInlineVisualOverflowBoundingBox() const {
 }
 
 LayoutRect LayoutInline::LinesVisualOverflowBoundingBox() const {
+  if (const NGPhysicalBoxFragment* box_fragment =
+          EnclosingBlockFlowFragmentOf(*this)) {
+    NGPhysicalOffsetRect result;
+    NGInlineFragmentIterator children(*box_fragment, this);
+    for (const auto& child : children) {
+      NGPhysicalOffsetRect child_rect =
+          child.fragment->VisualRectWithContents();
+      child_rect.offset += child.offset_to_container_box;
+      result.Unite(child_rect);
+    }
+    return result.ToLayoutRect();
+  }
+
   if (!AlwaysCreateLineBoxes())
     return CulledInlineVisualOverflowBoundingBox();