Dispel the myth that enclosingLayer can return zero

Source/core/rendering/RenderBlock.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 2331 matching lines @@
 void RenderBlock::paintSelection(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     if (shouldPaintSelectionGaps() && paintInfo.phase == PaintPhaseForeground) {
         LayoutUnit lastTop = 0;
         LayoutUnit lastLeft = logicalLeftSelectionOffset(this, lastTop);
         LayoutUnit lastRight = logicalRightSelectionOffset(this, lastTop);
         GraphicsContextStateSaver stateSaver(*paintInfo.context);
 
         LayoutRect gapRectsBounds = selectionGaps(this, paintOffset, LayoutSize(), lastTop, lastLeft, lastRight, &paintInfo);
         if (!gapRectsBounds.isEmpty()) {
-            if (RenderLayer* layer = enclosingLayer()) {
-                gapRectsBounds.moveBy(-paintOffset);
-                if (!hasLayer()) {
-                    LayoutRect localBounds(gapRectsBounds);
-                    flipForWritingMode(localBounds);
-                    gapRectsBounds = localToContainerQuad(FloatRect(localBounds), layer->renderer()).enclosingBoundingBox();
-                    if (layer->renderer()->hasOverflowClip())
-                        gapRectsBounds.move(layer->renderBox()->scrolledContentOffset());
-                }
-                layer->addBlockSelectionGapsBounds(gapRectsBounds);
+            RenderLayer* layer = enclosingLayer();
+            gapRectsBounds.moveBy(-paintOffset);
+            if (!hasLayer()) {
+                LayoutRect localBounds(gapRectsBounds);
+                flipForWritingMode(localBounds);
+                gapRectsBounds = localToContainerQuad(FloatRect(localBounds), layer->renderer()).enclosingBoundingBox();
+                if (layer->renderer()->hasOverflowClip())
+                    gapRectsBounds.move(layer->renderBox()->scrolledContentOffset());
             }
+            layer->addBlockSelectionGapsBounds(gapRectsBounds);
         }
     }
 }
 
 static void clipOutPositionedObjects(const PaintInfo* paintInfo, const LayoutPoint& offset, TrackedRendererListHashSet* positionedObjects)
 {
     if (!positionedObjects)
         return;
 
     TrackedRendererListHashSet::const_iterator end = positionedObjects->end();
@@ skipping 2667 matching lines @@
 void RenderBlock::showLineTreeAndMark(const InlineBox* markedBox1, const char* markedLabel1, const InlineBox* markedBox2, const char* markedLabel2, const RenderObject* obj) const
 {
     showRenderObject();
     for (const RootInlineBox* root = firstRootBox(); root; root = root->nextRootBox())
         root->showLineTreeAndMark(markedBox1, markedLabel1, markedBox2, markedLabel2, obj, 1);
 }
 
 #endif
 
 } // namespace WebCore