Add flag to enable immersive fullscreen for v2 apps

ash/wm/immersive_fullscreen_controller_unittest.cc

Index: ash/wm/immersive_fullscreen_controller_unittest.cc
diff --git a/ash/wm/immersive_fullscreen_controller_unittest.cc b/ash/wm/immersive_fullscreen_controller_unittest.cc
index c25f9ee2b6a587c85fc80b191d8bea68ab6d4241..9d0b21b69e35799329255d8bd1ba5dd72af44ed8 100644
--- a/ash/wm/immersive_fullscreen_controller_unittest.cc
+++ b/ash/wm/immersive_fullscreen_controller_unittest.cc
@@ -54,7 +54,7 @@ class MockImmersiveFullscreenControllerDelegate
   virtual void SetVisibleFraction(double visible_fraction) OVERRIDE {
     visible_fraction_ = visible_fraction;
   }
-  virtual std::vector<gfx::Rect> GetVisibleBoundsInScreen() OVERRIDE {
+  virtual std::vector<gfx::Rect> GetVisibleBoundsInScreen() const OVERRIDE {
     std::vector<gfx::Rect> bounds_in_screen;
     bounds_in_screen.push_back(top_container_view_->GetBoundsInScreen());
     return bounds_in_screen;