Re-enable integration tests (flutter#20947)

* Unskip expression evaluation integration tests for non-Windows

* Add additional into to skip comments

* Add missing import

Author: DanTup

packages/flutter_tools/test/integration/expression_evaluation_test.dart

@@ -6,6 +6,7 @@ import 'dart:async';
 
 import 'package:file/file.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/platform.dart';
 
 import 'package:vm_service_client/vm_service_client.dart';
 
@@ -107,8 +108,7 @@ void main() {
       await breakInBuildMethod(_flutter);
       await evaluateComplexReturningExpressions();
     });
-    // https://github.com/flutter/flutter/issues/17833
-    // The test appears to be flaky and time out some times, skipping while
-    // investigation is ongoing: https://github.com/flutter/flutter/issues/19542
-  }, timeout: const Timeout.factor(6), skip: true);
+    // TODO(dantup): Unskip after flutter-tester is fixed on Windows:
+    // https://github.com/flutter/flutter/issues/17833.
+  }, timeout: const Timeout.factor(6), skip: platform.isWindows);
 }

packages/flutter_tools/test/integration/flutter_attach_test.dart

@@ -38,6 +38,7 @@ void main() {
       await _flutterAttach.attach(_flutterRun.vmServicePort);
       await _flutterAttach.hotReload();
     });
-    // TODO(dantup): Unskip after https://github.com/flutter/flutter/issues/17833.
+    // TODO(dantup): Unskip after flutter-tester is fixed on Windows:
+    // https://github.com/flutter/flutter/issues/17833.
   }, timeout: const Timeout.factor(6), skip: platform.isWindows);
 }

packages/flutter_tools/test/integration/hot_reload_test.dart

@@ -32,7 +32,8 @@ void main() {
     test('works without error', () async {
       await _flutter.run();
       await _flutter.hotReload();
-      // TODO(dantup): Unskip after https://github.com/flutter/flutter/issues/17833.
+      // TODO(dantup): Unskip after flutter-tester is fixed on Windows:
+      // https://github.com/flutter/flutter/issues/17833.
     }, skip: platform.isWindows);
 
     test('hits breakpoints with file:// prefixes after reload', () async {
@@ -43,7 +44,12 @@ void main() {
           new Uri.file(_project.breakpointFile).toString(),
           _project.breakpointLine);
       expect(isolate.pauseEvent, isInstanceOf<VMPauseBreakpointEvent>());
-      // TODO(dantup): Unskip after https://github.com/flutter/flutter/issues/18441.
+      // TODO(dantup): Unskip for Mac when [1] is fixed, unskip on Windows when
+      // both [1] and [2] are fixed.
+      // [1] hot reload/breakpoints fail when uris prefixed with file://
+      //     https://github.com/flutter/flutter/issues/18441
+      // [2] flutter-tester doesn't work on Windows
+      //     https://github.com/flutter/flutter/issues/17833
     }, skip: !platform.isLinux);
   }, timeout: const Timeout.factor(6));
 }

packages/flutter_tools/test/integration/lifetime_test.dart

@@ -45,6 +45,7 @@ void main() {
       await new Future<void>.delayed(requiredLifespan);
       expect(_flutter.hasExited, equals(false));
     });
-    // TODO(dantup): Unskip after https://github.com/flutter/flutter/issues/17833.
+    // TODO(dantup): Unskip after flutter-tester is fixed on Windows:
+    // https://github.com/flutter/flutter/issues/17833.
   }, timeout: const Timeout.factor(6), skip: platform.isWindows);
 }