add transparency to navigation bar for image preview

src/main/java/com/owncloud/android/ui/preview/PreviewImageActivity.java

@@ -26,6 +26,7 @@ import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.ServiceConnection;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.IBinder;
 import android.support.v4.view.ViewPager;
@@ -33,6 +34,7 @@ import android.support.v4.widget.DrawerLayout;
 import android.support.v7.app.ActionBar;
 import android.view.MenuItem;
 import android.view.View;
+import android.view.WindowManager;
 
 import com.ortiz.touch.ExtendedViewPager;
 import com.owncloud.android.MainApp;
@@ -121,6 +123,12 @@ public class PreviewImageActivity extends FileActivity implements
                         }
                     }
                 });
+
+        // Add transparency to bottom navigation bar where supported
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
+            getWindow().setFlags(WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS,
+                    WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);
+        }
          
         if (savedInstanceState != null) {
             mRequestWaitingForBinder = savedInstanceState.getBoolean(KEY_WAITING_FOR_BINDER);