Simplify if-else block into single return statement (#175574)

Follow up of flutter/flutter#175396

This PR applies the code change suggestion from gemini review

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---------

Co-authored-by: Tong Mu <[email protected]>

Author: ValentinVignal

packages/flutter/test/material/scrollbar_test.dart

@@ -934,12 +934,9 @@ void main() {
             useMaterial3: false,
             scrollbarTheme: ScrollbarThemeData(
               thumbVisibility: WidgetStateProperty.all(true),
-              trackVisibility: WidgetStateProperty.resolveWith((Set<WidgetState> states) {
-                if (states.contains(WidgetState.hovered)) {
-                  return true;
-                }
-                return false;
-              }),
+              trackVisibility: WidgetStateProperty.resolveWith(
+                (Set<WidgetState> states) => states.contains(WidgetState.hovered),
+              ),
             ),
           ),
           home: const SingleChildScrollView(child: SizedBox(width: 4000.0, height: 4000.0)),
@@ -1086,12 +1083,9 @@ void main() {
             useMaterial3: false,
             scrollbarTheme: ScrollbarThemeData(
               thumbVisibility: WidgetStateProperty.all(true),
-              trackVisibility: WidgetStateProperty.resolveWith((Set<WidgetState> states) {
-                if (states.contains(WidgetState.hovered)) {
-                  return true;
-                }
-                return false;
-              }),
+              trackVisibility: WidgetStateProperty.resolveWith(
+                (Set<WidgetState> states) => states.contains(WidgetState.hovered),
+              ),
             ),
           ),
           home: const SingleChildScrollView(child: SizedBox(width: 4000.0, height: 4000.0)),
@@ -1154,12 +1148,9 @@ void main() {
             useMaterial3: false,
             scrollbarTheme: ScrollbarThemeData(
               thumbVisibility: WidgetStateProperty.all(true),
-              trackVisibility: WidgetStateProperty.resolveWith((Set<WidgetState> states) {
-                if (states.contains(WidgetState.hovered)) {
-                  return true;
-                }
-                return false;
-              }),
+              trackVisibility: WidgetStateProperty.resolveWith(
+                (Set<WidgetState> states) => states.contains(WidgetState.hovered),
+              ),
             ),
           ),
           home: const SingleChildScrollView(child: SizedBox(width: 4000.0, height: 4000.0)),

packages/flutter/test/material/scrollbar_theme_test.dart

@@ -38,12 +38,9 @@ void main() {
           theme: ThemeData(
             useMaterial3: false,
             scrollbarTheme: ScrollbarThemeData(
-              trackVisibility: WidgetStateProperty.resolveWith((Set<WidgetState> states) {
-                if (states.contains(WidgetState.hovered)) {
-                  return true;
-                }
-                return false;
-              }),
+              trackVisibility: WidgetStateProperty.resolveWith(
+                (Set<WidgetState> states) => states.contains(WidgetState.hovered),
+              ),
             ),
           ),
           home: ScrollConfiguration(
@@ -387,12 +384,9 @@ void main() {
           theme: ThemeData(
             colorScheme: const ColorScheme.light(),
             scrollbarTheme: ScrollbarThemeData(
-              trackVisibility: WidgetStateProperty.resolveWith((Set<WidgetState> states) {
-                if (states.contains(WidgetState.hovered)) {
-                  return true;
-                }
-                return false;
-              }),
+              trackVisibility: WidgetStateProperty.resolveWith(
+                (Set<WidgetState> states) => states.contains(WidgetState.hovered),
+              ),
             ),
           ),
           home: ScrollConfiguration(
@@ -492,12 +486,9 @@ void main() {
         final ScrollController scrollController = ScrollController();
         final ThemeData theme = appTheme.copyWith(
           scrollbarTheme: ScrollbarThemeData(
-            trackVisibility: WidgetStateProperty.resolveWith((Set<WidgetState> states) {
-              if (states.contains(WidgetState.hovered)) {
-                return true;
-              }
-              return false;
-            }),
+            trackVisibility: WidgetStateProperty.resolveWith(
+              (Set<WidgetState> states) => states.contains(WidgetState.hovered),
+            ),
           ),
         );
         return (
@@ -789,12 +780,9 @@ ScrollbarThemeData _scrollbarTheme({
     thickness: thickness ?? WidgetStateProperty.resolveWith(_getThickness),
     trackVisibility:
         trackVisibility ??
-        WidgetStateProperty.resolveWith((Set<WidgetState> states) {
-          if (states.contains(WidgetState.hovered)) {
-            return true;
-          }
-          return false;
-        }),
+        WidgetStateProperty.resolveWith(
+          (Set<WidgetState> states) => states.contains(WidgetState.hovered),
+        ),
     thumbVisibility: thumbVisibility,
     radius: radius,
     thumbColor: thumbColor ?? WidgetStateProperty.resolveWith(_getThumbColor),