Testcase for bug https://webkit.org/b/120726: When deleting editable content, typing style should be reset when moving into another node.

Deleting 'W' in blue color and then inserting 'O'. The following markup should show 'O' in blue color:
| "H "
| <font>
|   color="#0000ff"
|   <span>
|     style="caret-color: rgb(0, 0, 255);"
|     "O<#selection-caret>"

Deleting the blue colored text and the preceding space and then inserting 'W'. 'W' should be not be in blue color in the following markup:
| "HW<#selection-caret>"