Add feature flag for landscape orientation.

Signal/src/ViewControllers/MediaPageViewController.swift

@@ -145,7 +145,7 @@ class MediaPageViewController: UIPageViewController, UIPageViewControllerDataSou
         // e.g. when getting to media details via message details screen, there's only
         // one "Page" so the bounce doesn't make sense.
         pagerScrollView.isScrollEnabled = sliderEnabled
-        pagerScrollViewContentOffsetObservation = pagerScrollView.observe(\.contentOffset, options: [.new]) { [weak self] object, change in
+        pagerScrollViewContentOffsetObservation = pagerScrollView.observe(\.contentOffset, options: [.new]) { [weak self] _, change in
             guard let strongSelf = self else { return }
             strongSelf.pagerScrollView(strongSelf.pagerScrollView, contentOffsetDidChange: change)
         }
@@ -607,10 +607,16 @@ class MediaPageViewController: UIPageViewController, UIPageViewControllerDataSou
             return
         }
 
-        mediaGalleryDataSource.dismissMediaDetailViewController(self,
-                                                                animated: isAnimated,
-                                                                completion: completion)
-
+        if IsLandscapeOrientationEnabled() {
+            mediaGalleryDataSource.dismissMediaDetailViewController(self,
+                                                                    animated: isAnimated,
+                                                                    completion: completion)
+        } else {
+            mediaGalleryDataSource.dismissMediaDetailViewController(self, animated: isAnimated) {
+                UIDevice.current.ows_setOrientation(.portrait)
+                completion?()
+            }
+        }
     }
 
     // MARK: MediaDetailViewControllerDelegate

SignalMessaging/ViewControllers/OWSViewController.h

@@ -6,7 +6,7 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-#define LANDSCAPE_ORIENTATION_ENABLED
+BOOL IsLandscapeOrientationEnabled(void);
 
 UIInterfaceOrientationMask DefaultUIInterfaceOrientationMask(void);
 

SignalMessaging/ViewControllers/OWSViewController.m

@@ -8,13 +8,15 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+BOOL IsLandscapeOrientationEnabled(void)
+{
+    return NO;
+}
+
 UIInterfaceOrientationMask DefaultUIInterfaceOrientationMask(void)
 {
-#ifdef LANDSCAPE_ORIENTATION_ENABLED
-    return UIInterfaceOrientationMaskAllButUpsideDown;
-#else
-    return UIInterfaceOrientationMaskPortrait;
-#endif
+    return (IsLandscapeOrientationEnabled() ? UIInterfaceOrientationMaskAllButUpsideDown
+                                            : UIInterfaceOrientationMaskPortrait);
 }
 
 @interface OWSViewController ()