[1.5.4] Remove Semantics relatives

Runtime/cupertino/app.cs

             LocaleListResolutionCallback localeListResolutionCallback = null,
             LocaleResolutionCallback localeResolutionCallback = null,
             List<Locale> supportedLocales = null,
-            bool showPerformanceOverlay = false,
-            bool checkerboardRasterCacheImages = false,
-            bool checkerboardOffscreenLayers = false,
-            bool showSemanticsDebugger = false,
-            bool debugShowCheckedModeBanner = true
+            bool showPerformanceOverlay = false
-            D.assert(checkerboardRasterCacheImages != null);
-            D.assert(checkerboardOffscreenLayers != null);
-            D.assert(showSemanticsDebugger != null);
-            D.assert(debugShowCheckedModeBanner != null);
 
             supportedLocales = supportedLocales ?? new List<Locale> {new Locale("en", "US")};
             this.navigatorKey = navigatorKey;
             this.localeResolutionCallback = localeResolutionCallback;
             this.supportedLocales = supportedLocales;
             this.showPerformanceOverlay = showPerformanceOverlay;
-            this.checkerboardRasterCacheImages = checkerboardRasterCacheImages;
-            this.checkerboardOffscreenLayers = checkerboardOffscreenLayers;
-            this.showSemanticsDebugger = showSemanticsDebugger;
-            this.debugShowCheckedModeBanner = debugShowCheckedModeBanner;
         }
 
         public readonly GlobalKey<NavigatorState> navigatorKey;
         public readonly LocaleResolutionCallback localeResolutionCallback;
         public readonly List<Locale> supportedLocales;
         public readonly bool showPerformanceOverlay;
-        public readonly bool checkerboardRasterCacheImages;
-        public readonly bool checkerboardOffscreenLayers;
-        public readonly bool showSemanticsDebugger;
-        public readonly bool debugShowCheckedModeBanner;
 
         public override State createState() {
             return new _CupertinoAppState();
         public override Widget build(BuildContext context) {
             CupertinoThemeData effectiveThemeData = this.widget.theme ?? new CupertinoThemeData();
 
-            Widget _InspectorSelectButtonBuilder(BuildContext _context, VoidCallback onPressed) {
-                return CupertinoButton.filled(
-                    child: new Icon(
-                        CupertinoIcons.search,
-                        size: 28.0f,
-                        color: CupertinoColors.white
-                    ),
-                    padding: EdgeInsets.zero,
-                    onPressed: onPressed
-                );
-            }
-
             return new ScrollConfiguration(
                 behavior: new _AlwaysCupertinoScrollBehavior(),
                 child: new CupertinoTheme(
                         localeListResolutionCallback: this.widget.localeListResolutionCallback,
                         supportedLocales: this.widget.supportedLocales,
                         showPerformanceOverlay: this.widget.showPerformanceOverlay,
-                        checkerboardRasterCacheImages: this.widget.checkerboardRasterCacheImages,
-                        checkerboardOffscreenLayers: this.widget.checkerboardOffscreenLayers,
-                        showSemanticsDebugger: this.widget.showSemanticsDebugger,
-                        debugShowCheckedModeBanner: this.widget.debugShowCheckedModeBanner,
-                        inspectorSelectButtonBuilder: _InspectorSelectButtonBuilder
+                        inspectorSelectButtonBuilder: (BuildContext _context, VoidCallback onPressed) => {
+                            return CupertinoButton.filled(
+                                child: new Icon(
+                                    CupertinoIcons.search,
+                                    size: 28.0f,
+                                    color: CupertinoColors.white
+                                ),
+                                padding: EdgeInsets.zero,
+                                onPressed: onPressed
+                            );
+                        }
                     )
                 )
             );

Runtime/widgets/app.cs

         public readonly string title;
         public readonly GenerateAppTitle onGenerateTitle;
         public readonly Color color;
-        public readonly bool checkerboardRasterCacheImages;
-        public readonly bool checkerboardOffscreenLayers;
-        public readonly bool showSemanticsDebugger;
-        public readonly bool debugShowCheckedModeBanner;
         public readonly InspectorSelectButtonBuilder inspectorSelectButtonBuilder;
 
         public WidgetsApp(
             GenerateAppTitle onGenerateTitle = null,
             string title = "",
             Color color = null,
-            bool checkerboardRasterCacheImages = false,
-            bool checkerboardOffscreenLayers = false,
-            bool showSemanticsDebugger = false,
-            bool debugShowCheckedModeBanner = true,
             InspectorSelectButtonBuilder inspectorSelectButtonBuilder = null
         ) : base(key) {
             routes = routes ?? new Dictionary<string, WidgetBuilder>();
             this.onGenerateTitle = onGenerateTitle;
             this.title = title;
             this.color = color;
-            this.checkerboardRasterCacheImages = checkerboardRasterCacheImages;
-            this.checkerboardOffscreenLayers = checkerboardOffscreenLayers;
-            this.showSemanticsDebugger = showSemanticsDebugger;
-            this.debugShowCheckedModeBanner = debugShowCheckedModeBanner;
             this.inspectorSelectButtonBuilder = inspectorSelectButtonBuilder;
 
             D.assert(