Fix Linux/Gtk build after r248965 with gcc 4.8

Fix Linux/Gtk build after r248965 with gcc 4.8. The compiler was complaining
about DevToolsContentsResizingStrategy not being copyable. Using a if/else
instead of a ternary makes the compiler happy.

R=thakis@chromium.org

Review URL: https://codereview.chromium.org/130633008

Patch from Chris Dumez <ch.dumez@samsung.com>.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249164 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249164