fix FileImage error and and float compare func

Samples/UIWidgetsSamples_2019_4/Assets/UIWidgetsGallery/demo/shrine/expanding_bottom_sheet.cs

           new Row(
             children: new List<Widget>
             {
-             /* new AnimatedPadding(
+              new AnimatedPadding(
-              ),*/
+              ),
               new Container(
                 // Accounts for the overflow number
                 width: numProducts > 3 ? _width - 94.0f : _width - 64.0f,
-              )//, new ExtraProductsNumber(),
+              ), 
+              new ExtraProductsNumber(),
             }
           ),
         }

com.unity.uiwidgets/Runtime/animation/animation_controller.cs

 
         void _internalSetValue(float newValue) {
             _value = newValue.clamp(lowerBound, upperBound);
-            if (_value == lowerBound) {
+            if (foundation_.FloatEqual(_value, lowerBound)) {
-            else if (_value == upperBound) {
+            else if (foundation_.FloatEqual(_value, upperBound)) {
                 _status = AnimationStatus.completed;
             }
             else {

com.unity.uiwidgets/Runtime/foundation/diagnostics.cs

         public static bool _isSingleLine(DiagnosticsTreeStyle? style) {
             return style == DiagnosticsTreeStyle.singleLine;
         }
+
+        public static bool FloatEqual(float left, float right) {
+            return Mathf.Abs(left - right) < precisionErrorTolerance;
+        }
     }
 
 

com.unity.uiwidgets/Runtime/material/app_bar.cs

                                 child: appBar
                             )
                         ),
-                        widget.bottomOpacity == 1.0f
+                        foundation_.FloatEqual(widget.bottomOpacity, 1.0f)
                             ? (Widget) widget.bottom
                             : new Opacity(
                                 opacity: new Interval(0.25f, 1.0f, curve: Curves.fastOutSlowIn).transform(widget

com.unity.uiwidgets/Runtime/material/app_bar_theme.cs

         public bool Equals(AppBarTheme other) {
             return other.brightness == brightness
                    && other.color == color
-                   && other.elevation == elevation
+                   && Equals(other.elevation, elevation)
                    && other.iconTheme == iconTheme
                    && other.actionsIconTheme == actionsIconTheme
                    && other.textTheme == textTheme;

com.unity.uiwidgets/Runtime/painting/image_provider.cs

         public readonly float scale;
 
         public override Future<FileImage> obtainKey(ImageConfiguration configuration) {
-            return Future.value(FutureOr.value(this)).to<FileImage>();
+            return new SynchronousFuture<FileImage>(this);
         }
 
         public override ImageStreamCompleter load(FileImage key, DecoderCallback decode) {