Remove "unnecessary" imports. (#74820)

examples/image_list/lib/main.dart

@@ -7,7 +7,6 @@ import 'dart:io';
 import 'dart:math';
 import 'dart:typed_data';
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart' show rootBundle;
 import 'package:flutter/services.dart';
 
 /// An example that sets up local http server for serving single

examples/layers/raw/shader_warm_up.dart

@@ -7,7 +7,6 @@
 import 'dart:ui' as ui;
 
 import 'package:flutter/material.dart';
-import 'package:flutter/painting.dart' show DefaultShaderWarmUp;
 
 Future<void> beginFrame(Duration timeStamp) async {
   // PAINT

examples/layers/rendering/src/sector_layout.dart

@@ -5,7 +5,6 @@
 import 'dart:math' as math;
 
 import 'package:flutter/rendering.dart';
-import 'package:flutter/gestures.dart';
 
 const double kTwoPi = 2 * math.pi;
 

examples/layers/rendering/src/solid_color_box.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'package:flutter/rendering.dart';
-import 'package:flutter/gestures.dart';
 
 class RenderSolidColorBox extends RenderDecoratedBox {
   RenderSolidColorBox(this.backgroundColor, { this.desiredSize = Size.infinite })

examples/layers/test/sector_layout_test.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'package:flutter/gestures.dart';
-import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/src/sector_layout.dart';

examples/layers/widgets/sectors.dart

@@ -5,7 +5,6 @@
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
-import 'package:flutter/rendering.dart';
 
 import '../rendering/src/sector_layout.dart';