[crash] Renderer crashes when spell checking a disabled input field.

[crash] Renderer crashes when spell checking a disabled input field.
https://bugs.webkit.org/show_bug.cgi?id=75941

Patch by Shinya Kawanaka <shinyak@google.com> on 2012-01-16
Reviewed by Hajime Morita.

.:

* ManualTests/editing-disabled-node-replace-crash.html: Added.

Source/WebCore:

We confirm the selection is editable before replacing text.

Tests: ManualTests/editing-disabled-node-replace-crash.html

* editing/Editor.cpp:
(WebCore::Editor::replaceSelectionWithFragment):
* editing/ReplaceSelectionCommand.cpp:
(WebCore::ReplaceSelectionCommand::doApply):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@105050 268f45cc-cd09-0410-ab3c-d52691b4dbfc