Clear SVGInlineTextBox fragments when the text changes.

Source/core/rendering/svg/SVGInlineTextBox.cpp

 /**
  * Copyright (C) 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 50 matching lines @@
     , m_paintingResource(0)
 {
 }
 
 void SVGInlineTextBox::dirtyLineBoxes()
 {
     InlineTextBox::dirtyLineBoxes();
 
     // Clear the now stale text fragments
     clearTextFragments();
+
+    // And clear any following text fragments as the text on which they

[eseidel, 2013/05/15 18:35:01]

This doesn't feel right.  In CSS the block handles clearling of whole lines
(Root Line Boxes) and lineboxes don't mark each other as dirty to my knowledge. 
Should the linebox really have this knowledge?

[Stephen Chennney, 2013/05/15 19:16:46]

SVG creates InlineTextBoxes for reasons that differ from HTML, to handle
situations like per-character offsets. These all need to be cleared when the
text changes to invalidate the fragment lists inside them (which hold
information about the string).

Under certain conditions, like this bug, the root line box is not marked dirty -
I verified that before applying this fix. If you think the code in
RenderText::setTextWithOffset is wrong to not always mark the root box as dirty,
then I can change that. The particular line that prevents the root box from
being dirtied is RenderText.cpp:1288.

+    // depend may now no longer exist.
+    InlineTextBox* nextBox = nextTextBox();
+    if (nextBox)
+        nextBox->dirtyLineBoxes();
 }
 
 int SVGInlineTextBox::offsetForPosition(float, bool) const
 {
     // SVG doesn't use the standard offset <-> position selection system, as it's not suitable for SVGs complex needs.
     // vertical text selection, inline boxes spanning multiple lines (contrary to HTML, etc.)
     ASSERT_NOT_REACHED();
     return 0;
 }
 
@@ skipping 639 matching lines @@
                     return true;
              }
         }
     }
     return false;
 }
 
 } // namespace WebCore
 
 #endif