Fix compile warnings in Panel.xib

XIB changes: 
- removed "Single Line" attribute from NSTextField (we don't need it since we set NSTextField to Layout:Truncate, LineBreaks:TruncateTail in IB so it does not wrap/scroll)
- removed obsolete outlets that do not exist in the code
- removed autosizing masks for controls we layout from code anyways

Moved PanelWindowCocoaImpl declaration into .h file so the IB can see it.

The XIB now compiles w/o warnings and the layout code is more consistent (all controls are laid out in the similar way in code)

BUG=120539

Review URL: http://codereview.chromium.org/9969025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@130457 0039d316-1c4b-4281-b951-d872f2087c98
4 files changed