Fix Memory leaks on Browser application

Working on Issue 31125 (http://code.google.com/p/android/issues
/detail?id=31125):
* Enhance mTabViews management on NavScreen class (add remove()
function when necessary).

Change-Id: I89662880107ae88ead40d5246286d4ab65ed9e75
Signed-off-by: Sebastien MICHEL <sebastien.michel@intel.com>