In WebKit TinyMCE may remove all spans when merging nodes with backspace

[azaozz]

To reproduce:

• Make a test post with couple of paragraphs.
• Add some text colors (to a word or whole sentence). The colors are added as <span style="color:..."> around the selected text.
• At the end of the post, press Enter and then immediately press backspace.

At this point all text colors disappear. Looking at the html, all spans have been stripped from the content. Caused by the fix for WebKit quirk with backspace (WebKit inserts lots of junk when merging the nodes on backspace).

This was fixed upstream: ​https://github.com/tinymce/tinymce/commit/113bd1ceaef1e1de5f2fdf54633d58424817182c

This is related to #22766 and will fix it as well. Thinking we should backport that patch and update TinyMCE in 3.5.1 (moving to 3.5.1 milestone for consideration).

23010.patch​ contains the latest git version of TinyMCE.

In 23192:

TinyMCE: update to latest source including the WebKit backspace fix, see #23010

This build of TinyMCE includes the following changes from 3.5.8:

• ​Fixed bug where focusing out of the body of the editor wouldn't properly add an undo level. Fixed issue with warning message being displayed on IE 9+ about the meta header fix for IE 8.
• ​Fixed bug where applying ins/del as inline elements would apply them as blocks.
• ​Keyboard navigation improvements.
• ​Added a different workaround for the WebKit delete/backspace bug

In 23217:

TinyMCE: update to latest source including the WebKit backspace fix, fixes #23010, fixes #22766 for 3.5