avoid mark viewMetrics dirty in update, which will potentially leads to frequent native-calls

Author: zhuxingwei

Runtime/editor/editor_utils.cs

@@ -31,6 +31,10 @@ public void Update() {
         public void OnEnable() {
             this._lastDevicePixelRatio = GameViewUtil.getGameViewDevicePixelRatio();
         }
+
+        public void onViewMetricsChanged() {
+            
+        }
 
         public float devicePixelRatio {
             get { return this._lastDevicePixelRatio; }

Runtime/engine/DisplayMetrics.cs

@@ -25,6 +25,7 @@ public interface DisplayMetrics {
         void OnEnable();
         void OnGUI();
         void Update();
+        void onViewMetricsChanged();
 
         float devicePixelRatio { get; }
 
@@ -46,11 +47,14 @@ public void OnGUI() {
         }
 
         public void Update() {
+            
+        }
+
+        public void onViewMetricsChanged() {
             //view metrics marks dirty
             this._viewMetrics = null;
         }
 
-
         public float devicePixelRatio {
             get {
                 if (this._devicePixelRatio > 0) {

Runtime/engine/UIWidgetsPanel.cs

@@ -130,7 +130,7 @@ bool _mouseEntered {
 
         void _handleViewMetricsChanged(string method, List<JSONNode> args) {
             this._windowAdapter.onViewMetricsChanged();
-            this._displayMetrics.Update();
+            this._displayMetrics.onViewMetricsChanged();
         }
 
         protected override void OnEnable() {