Clear SVGInlineTextBox fragments when the text changes.

Source/core/rendering/svg/SVGInlineTextBox.cpp

Index: Source/core/rendering/svg/SVGInlineTextBox.cpp
diff --git a/Source/core/rendering/svg/SVGInlineTextBox.cpp b/Source/core/rendering/svg/SVGInlineTextBox.cpp
index 685fa18419dd2de509fbb0300a94e1c681e188cb..13e6802a2ba3d8f3fd841bc1b782555971363b8b 100644
--- a/Source/core/rendering/svg/SVGInlineTextBox.cpp
+++ b/Source/core/rendering/svg/SVGInlineTextBox.cpp
@@ -68,6 +68,12 @@ void SVGInlineTextBox::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