Disable newline selection highlighting for vertical and RTL text.

Source/core/paint/InlineTextBoxPainter.cpp

Index: Source/core/paint/InlineTextBoxPainter.cpp
diff --git a/Source/core/paint/InlineTextBoxPainter.cpp b/Source/core/paint/InlineTextBoxPainter.cpp
index 7a30e8d931ece2f37b4ec446d42c8b5d6c7ab52a..35606d9ecc33e1b9fe80834e86a111bda276e557 100644
--- a/Source/core/paint/InlineTextBoxPainter.cpp
+++ b/Source/core/paint/InlineTextBoxPainter.cpp
@@ -253,7 +253,9 @@ bool InlineTextBoxPainter::shouldPaintTextBox(const PaintInfo& paintInfo)
     // This code path is only called in PaintPhaseForeground whereas we would
     // expect PaintPhaseSelection. The existing haveSelection logic in paint()
     // tests for != PaintPhaseTextClip.
-    bool paintLineBreaks = RuntimeEnabledFeatures::selectionPaintingWithoutSelectionGapsEnabled();
+    bool paintLineBreaks = RuntimeEnabledFeatures::selectionPaintingWithoutSelectionGapsEnabled()
+        // TODO(wkorman): Remove horizontal restriction once vertical text is operational.
+        && m_inlineTextBox.isHorizontal();
     if ((!paintLineBreaks && m_inlineTextBox.isLineBreak())
         || !paintInfo.shouldPaintWithinRoot(&m_inlineTextBox.layoutObject())
         || m_inlineTextBox.layoutObject().style()->visibility() != VISIBLE