Use a dual pane layout instead of the navigation drawer for sw600dp screens or larger.

PS2: mActionBar should be assigned regardless of whether mDrawerLayout is null.

PS3: Use dual-pane layout when in landscape orientaiton.

Change-Id: If2c96cda691bab50ebd5d869f910a9351973367b
Merge "Use a dual pane layout instead of the navigation drawer for sw600dp screens or larger." into jb-mr2