Merge pull request #307 from UnityTech/master

release stable version 1.5.4

Author: zhuxingwei

Runtime/Plugins/platform/ios/DeviceScreen.mm

@@ -1,8 +1,13 @@
 #import <UIKit/UIKit.h>
+#import "UIWidgetsDevice.h"
 extern "C"
 {
-    int IOSDeviceScaleFactor()
+    float IOSDeviceScaleFactor()
     {
-        return [[UIScreen mainScreen] scale];
+        float scale = [[UIScreen mainScreen] scale] * 1.0;
+        if ([UIWidgetsDevice NeedScreenDownSample]) {
+            scale *= 0.8696;
+        }
+        return scale;
     }
 }