Disable newline selection highlighting for vertical and RTL text.

Source/core/paint/InlineTextBoxPainter.cpp

 // Copyright 2014 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 "config.h"
 #include "core/paint/InlineTextBoxPainter.h"
 
 #include "core/editing/CompositionUnderline.h"
 #include "core/editing/Editor.h"
 #include "core/editing/markers/DocumentMarkerController.h"
@@ skipping 235 matching lines @@
 bool InlineTextBoxPainter::shouldPaintTextBox(const PaintInfo& paintInfo)
 {
     // When painting selection, we want to include a highlight when the
     // selection spans line breaks. In other cases such as invisible elements
     // or those with no text that are not line breaks, we can skip painting
     // wholesale.
     // TODO(wkorman): Constrain line break painting to appropriate paint phase.
     // 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 and RTL restrictions once operational.
+        && m_inlineTextBox.isHorizontal()
+        && m_inlineTextBox.isLeftToRightDirection();
     if ((!paintLineBreaks && m_inlineTextBox.isLineBreak())
         || !paintInfo.shouldPaintWithinRoot(&m_inlineTextBox.layoutObject())
         || m_inlineTextBox.layoutObject().style()->visibility() != VISIBLE
         || m_inlineTextBox.truncation() == cFullTruncation
         || !m_inlineTextBox.len())
         return false;
     return true;
 }
 
 unsigned InlineTextBoxPainter::underlinePaintStart(const CompositionUnderline& underline)
@@ skipping 575 matching lines @@
             LayoutPoint textOrigin(boxOrigin.x(), boxOrigin.y() + font.fontMetrics().ascent());
             TextPainter textPainter(pt, font, run, textOrigin, boxRect, m_inlineTextBox.isHorizontal());
 
             textPainter.paint(sPos, ePos, length, textStyle, 0);
         }
     }
 }
 
 
 } // namespace blink