[Gallery] Fix directory structure (#312)

gallery/lib/codeviewer/code_displayer.dart

@@ -0,0 +1,7 @@
+// Copyright 2019 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+typedef TextSpan CodeDisplayer(BuildContext context);

gallery/lib/codeviewer/code_style.dart

@@ -0,0 +1,43 @@
+// Copyright 2019 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+class CodeStyle extends InheritedWidget {
+  const CodeStyle({
+    this.baseStyle,
+    this.numberStyle,
+    this.commentStyle,
+    this.keywordStyle,
+    this.stringStyle,
+    this.punctuationStyle,
+    this.classStyle,
+    this.constantStyle,
+    @required Widget child,
+  }) : super(child: child);
+
+  final TextStyle baseStyle;
+  final TextStyle numberStyle;
+  final TextStyle commentStyle;
+  final TextStyle keywordStyle;
+  final TextStyle stringStyle;
+  final TextStyle punctuationStyle;
+  final TextStyle classStyle;
+  final TextStyle constantStyle;
+
+  static CodeStyle of(BuildContext context) {
+    return context.dependOnInheritedWidgetOfExactType<CodeStyle>();
+  }
+
+  @override
+  bool updateShouldNotify(CodeStyle oldWidget) =>
+      oldWidget.baseStyle != baseStyle ||
+      oldWidget.numberStyle != numberStyle ||
+      oldWidget.commentStyle != commentStyle ||
+      oldWidget.keywordStyle != keywordStyle ||
+      oldWidget.stringStyle != stringStyle ||
+      oldWidget.punctuationStyle != punctuationStyle ||
+      oldWidget.classStyle != classStyle ||
+      oldWidget.constantStyle != constantStyle;
+}