Clear SVGInlineTextBox fragments when the text changes.

Clear SVGInlineTextBox fragments when the text changes.
https://bugs.webkit.org/show_bug.cgi?id=130879

Reviewed by Darin Adler.

Blink: https://src.chromium.org/viewvc/blink?revision=150456&view=revision
Source/WebCore:

This patch modifies SVGInlineTextBox::dirtyLineBoxes to clear all
following text boxes when invoked. Typically this method is called
when the underlying text string changes, and that change needs to
be propagated to all the boxes that use the text beyond the point
where the text is first modified.

Also cleans up final function keywords for SVGRootInlineBox.

Test: svg/custom/unicode-in-tspan-multi-svg-crash.html

* rendering/InlineTextBox.h: Added (non-recursive) dirtyOwnLineBoxes() function
(WebCore::InlineTextBox::dirtyOwnLineBoxes): Calls dirtyLineBoxes()
* rendering/svg/SVGInlineTextBox.h: Added (non-recursive) dirtyOwnLineBoxes() function
(WebCore::SVGInlineTextBox::dirtyOwnLineBoxes):
* rendering/svg/SVGInlineTextBox.cpp:
(WebCore::SVGInlineTextBox::dirtyOwnLineBoxes): Non-recursive part of dirtyLineBoxes()
(WebCore::SVGInlineTextBox::dirtyLineBoxes): Calls dirtyOwnLineBoxes() in a loop
* rendering/svg/SVGRootInlineBox.h:

LayoutTests:

When failing, this test will render garbage characters or crash.

* svg/custom/unicode-in-tspan-multi-svg-crash-expected.txt: Added.
* svg/custom/unicode-in-tspan-multi-svg-crash.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@166420 268f45cc-cd09-0410-ab3c-d52691b4dbfc