[Gallery] Tweak banner colors (#311)

gallery/gallery/lib/codeviewer/code_segments.dart

@@ -221,6 +221,19 @@ class CodeSegments {
       TextSpan(style: codeStyle.punctuationStyle, text: '{'),
       TextSpan(style: codeStyle.baseStyle, text: '\u000a    '),
       TextSpan(style: codeStyle.keywordStyle, text: 'final'),
+      TextSpan(style: codeStyle.baseStyle, text: ' colorScheme '),
+      TextSpan(style: codeStyle.punctuationStyle, text: '='),
+      TextSpan(style: codeStyle.baseStyle, text: ' '),
+      TextSpan(style: codeStyle.classStyle, text: 'Theme'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'of'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '('),
+      TextSpan(style: codeStyle.baseStyle, text: 'context'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ').'),
+      TextSpan(style: codeStyle.baseStyle, text: 'colorScheme'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ';'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a    '),
+      TextSpan(style: codeStyle.keywordStyle, text: 'final'),
       TextSpan(style: codeStyle.baseStyle, text: ' banner '),
       TextSpan(style: codeStyle.punctuationStyle, text: '='),
       TextSpan(style: codeStyle.baseStyle, text: ' '),
@@ -255,19 +268,18 @@ class CodeSegments {
       TextSpan(style: codeStyle.classStyle, text: 'Icons'),
       TextSpan(style: codeStyle.punctuationStyle, text: '.'),
       TextSpan(style: codeStyle.baseStyle, text: 'access_alarm'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ','),
+      TextSpan(style: codeStyle.baseStyle, text: ' color'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ':'),
+      TextSpan(style: codeStyle.baseStyle, text: ' colorScheme'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'onPrimary'),
       TextSpan(style: codeStyle.punctuationStyle, text: '),'),
       TextSpan(
           style: codeStyle.baseStyle,
           text: '\u000a              backgroundColor'),
       TextSpan(style: codeStyle.punctuationStyle, text: ':'),
-      TextSpan(style: codeStyle.baseStyle, text: ' '),
-      TextSpan(style: codeStyle.classStyle, text: 'Theme'),
-      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
-      TextSpan(style: codeStyle.baseStyle, text: 'of'),
-      TextSpan(style: codeStyle.punctuationStyle, text: '('),
-      TextSpan(style: codeStyle.baseStyle, text: 'context'),
-      TextSpan(style: codeStyle.punctuationStyle, text: ').'),
-      TextSpan(style: codeStyle.baseStyle, text: 'colorScheme'),
+      TextSpan(style: codeStyle.baseStyle, text: ' colorScheme'),
       TextSpan(style: codeStyle.punctuationStyle, text: '.'),
       TextSpan(style: codeStyle.baseStyle, text: 'primary'),
       TextSpan(style: codeStyle.punctuationStyle, text: ','),
@@ -369,6 +381,12 @@ class CodeSegments {
       TextSpan(style: codeStyle.punctuationStyle, text: '),'),
       TextSpan(style: codeStyle.baseStyle, text: '\u000a      '),
       TextSpan(style: codeStyle.punctuationStyle, text: '],'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a      backgroundColor'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ':'),
+      TextSpan(style: codeStyle.baseStyle, text: ' colorScheme'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'background'),
+      TextSpan(style: codeStyle.punctuationStyle, text: ','),
       TextSpan(style: codeStyle.baseStyle, text: '\u000a    '),
       TextSpan(style: codeStyle.punctuationStyle, text: ');'),
       TextSpan(style: codeStyle.baseStyle, text: '\u000a\u000a    '),

gallery/gallery/lib/demos/material/banner_demo.dart

@@ -44,12 +44,13 @@ class _BannerDemoState extends State<BannerDemo> {
 
   @override
   Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
     final banner = MaterialBanner(
       content: Text(GalleryLocalizations.of(context).bannerDemoText),
       leading: _showLeading
           ? CircleAvatar(
-              child: Icon(Icons.access_alarm),
-              backgroundColor: Theme.of(context).colorScheme.primary,
+              child: Icon(Icons.access_alarm, color: colorScheme.onPrimary),
+              backgroundColor: colorScheme.primary,
             )
           : null,
       actions: [
@@ -71,6 +72,7 @@ class _BannerDemoState extends State<BannerDemo> {
             },
           ),
       ],
+      backgroundColor: colorScheme.background,
     );
 
     return Scaffold(