Verifies that find and replace does not change matches in noneditable content. This test requires WebKitTestRunner.

After replacing 'eta' with '_eta_':
| "
        "
| <p>
|   contenteditable="false"
|   "alpha beta."
| "
        "
| <p>
|   "gamma b<#selection-anchor>_eta_<#selection-focus> phi."
| "
        "
| <div>
|   contenteditable="false"
|   "
            "
|   <p>
|     "alpha kappa eta."
|   "
            "
|   <p>
|     contenteditable="true"
|     "_eta_ kappa nu."
|   "
        "
| "
        "
| <p>
|   "b_eta_ phi delta."
| "
    "