Support <input webkitdirectory> in KDE file chooser

Support <input webkitdirectory> in KDE file chooser

Currently NOTREACHED() is reached when the KDE file chooser is active.

TEST=Manually:
1. Start Chrome in a KDE environment
2. Visit data:text/html,<input type=file webkitdirectory>
3. Click on the file chooser and select any directory.
4. In KDE environments, NOTREACHED() is reached.

5. Repeat the same steps with the env var NO_CHROME_KDE_FILE_DIALOG=1,
   and observe that NOTREACHED() is not reached any more, because the
   gtk fallback is used (which works correctly since r240564).

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=287863

[Elliot Glaysher, 2014-08-06 20:01:47]

lgtm

[commit-bot: I haz the power, 2014-08-06 20:04:06]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/rob@robwu.nl/445883002/1

[commit-bot: I haz the power, 2014-08-06 21:33:29]

Change committed as 287863