fix:rename the files

engine/Build.bee.cs

                 "src/shell/platform/unity/darwin/ios/cocoa_task_runner.h",
                 "src/shell/platform/unity/darwin/ios/unity_surface_manager.mm",
                 "src/shell/platform/unity/darwin/ios/unity_surface_manager.h",
-                "src/shell/platform/unity/darwin/ios/DeviceScreen.mm",
-                "src/shell/platform/unity/darwin/ios/UIWidgetsDevice.mm",
-                "src/shell/platform/unity/darwin/ios/UIWidgetsDevice.h",
+                "src/shell/platform/unity/darwin/ios/device_screen.mm",
+                "src/shell/platform/unity/darwin/ios/uiwidgets_device.mm",
+                "src/shell/platform/unity/darwin/ios/uiwidgets_device.h",
         };
 
         np.Sources.Add(c => IsWindows(c), winSources);

engine/src/shell/platform/unity/darwin/ios/uiwidgets_device.mm

-//
-//  UIWidgetsDevice.m
-//  Unity-iPhone
-//
-//  Created by Xingwei Zhu on 2019/6/24.
-//
-#include "UIWidgetsDevice.h"
+#include "uiwidgets_device.h"
 #import <sys/utsname.h>
 #import <UIKit/UIKit.h>
 

engine/src/shell/platform/unity/darwin/ios/device_screen.mm

+#import <UIKit/UIKit.h>
+#import "uiwidgets_device.h"
+#include "runtime/mono_api.h"
+
+namespace uiwidgets {
+
+    UIWIDGETS_API(float) IOSDeviceScaleFactor()
+    {
+        float scale = [[UIScreen mainScreen] scale] * 1.0;
+        if ([UIWidgetsDevice NeedScreenDownSample]) {
+            scale *= 0.8696;
+        }
+        return scale;
+    }
+}

engine/src/shell/platform/unity/darwin/ios/uiwidgets_device.h

+#ifndef UIWidgetsDevice_h
+#define UIWidgetsDevice_h
+
+#import <UIKit/UIKit.h>
+
+@interface UIWidgetsDevice : NSObject
+
++(NSString *) deviceName;
+
++(BOOL) NeedScreenDownSample;
+
+@end
+
+#endif

engine/src/shell/platform/unity/darwin/ios/DeviceScreen.mm

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

engine/src/shell/platform/unity/darwin/ios/UIWidgetsDevice.h

-//
-//  UIWidgetsDevice.h
-//  Unity-iPhone
-//
-//  Created by Xingwei Zhu on 2019/6/24.
-//
-
-#ifndef UIWidgetsDevice_h
-#define UIWidgetsDevice_h
-
-#import <UIKit/UIKit.h>
-
-@interface UIWidgetsDevice : NSObject
-
-+(NSString *) deviceName;
-
-+(BOOL) NeedScreenDownSample;
-
-@end
-
-#endif /* UIWidgetsDevice_h */