Split common matcher into its own file. (#12622)

This aids in running the tests internally in Google
since the libraries upon which tests depend and the
test files themselves are defined separately.

packages/flutter/test/painting/circle_border_test.dart

@@ -6,54 +6,7 @@ import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/mock_canvas.dart';
-
-final Matcher isUnitCircle = isPathThat(
-  includes: <Offset>[
-    const Offset(-0.6035617555492896, 0.2230970398703236),
-    const Offset(-0.7738478165627277, 0.5640447581420576),
-    const Offset(-0.46090034164788385, -0.692017006684612),
-    const Offset(-0.2138540316101296, -0.09997005339529785),
-    const Offset(-0.46919827227410416, 0.29581721423767027),
-    const Offset(-0.43628713652733153, 0.5065324817995975),
-    const Offset(0.0, 0.0),
-    const Offset(0.49296904381712725, -0.5922438805080081),
-    const Offset(0.2901141594861445, -0.3181478162967859),
-    const Offset(0.45229946324502146, 0.4324593232323706),
-    const Offset(0.11827752132593572, 0.806442226027837),
-    const Offset(0.8854165569581154, -0.08604230149167624),
-  ],
-  excludes: <Offset>[
-    const Offset(-100.0, -100.0),
-    const Offset(-100.0, 100.0),
-    const Offset(-1.1104403014186688, -1.1234939207590569),
-    const Offset(-1.1852827482514838, -0.5029551986333607),
-    const Offset(-1.0253256532179804, -0.02034402043932526),
-    const Offset(-1.4488532714237397, 0.4948740308904742),
-    const Offset(-1.03142206223176, 0.81070400258819),
-    const Offset(-1.006747917852356, 1.3712062218039343),
-    const Offset(-0.5241429900291878, -1.2852518410112541),
-    const Offset(-0.8879593765104428, -0.9999680025850874),
-    const Offset(-0.9120835110799488, -0.4361605900585557),
-    const Offset(-0.8184877240407303, 1.1202520775469589),
-    const Offset(-0.15746058420492282, -1.1905035795387513),
-    const Offset(-0.11519948876183506, 1.3848147258237393),
-    const Offset(0.0035741796943844495, -1.3383908620447724),
-    const Offset(0.34408827443814394, 1.4514436242950461),
-    const Offset(0.709487222145941, -1.3468012918181573),
-    const Offset(0.6287522653614315, -0.8315879623940617),
-    const Offset(0.9716071801865485, 0.24311969613525442),
-    const Offset(0.7632982576031955, 0.8329765574976169),
-    const Offset(0.9923766847309081, 1.0592617071813715),
-    const Offset(1.2696730082820435, -1.0353385446957046),
-    const Offset(1.4266154921521208, -0.8382633931857755),
-    const Offset(1.298035226938996, -0.11544603567954526),
-    const Offset(1.4143230992455558, 0.10842501221141165),
-    const Offset(1.465352952354424, 0.6999947490821032),
-    const Offset(1.0462985816010146, 1.3874230508561505),
-    const Offset(100.0, -100.0),
-    const Offset(100.0, 100.0),
-  ],
-);
+import 'common_matchers.dart';
 
 void main() {
   test('CircleBorder', () {

packages/flutter/test/painting/common_matchers.dart

+// Copyright 2017 The Chromium Authors. 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/painting.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import '../rendering/mock_canvas.dart';
+
+final Matcher isUnitCircle = isPathThat(
+  includes: <Offset>[
+    const Offset(-0.6035617555492896, 0.2230970398703236),
+    const Offset(-0.7738478165627277, 0.5640447581420576),
+    const Offset(-0.46090034164788385, -0.692017006684612),
+    const Offset(-0.2138540316101296, -0.09997005339529785),
+    const Offset(-0.46919827227410416, 0.29581721423767027),
+    const Offset(-0.43628713652733153, 0.5065324817995975),
+    const Offset(0.0, 0.0),
+    const Offset(0.49296904381712725, -0.5922438805080081),
+    const Offset(0.2901141594861445, -0.3181478162967859),
+    const Offset(0.45229946324502146, 0.4324593232323706),
+    const Offset(0.11827752132593572, 0.806442226027837),
+    const Offset(0.8854165569581154, -0.08604230149167624),
+  ],
+  excludes: <Offset>[
+    const Offset(-100.0, -100.0),
+    const Offset(-100.0, 100.0),
+    const Offset(-1.1104403014186688, -1.1234939207590569),
+    const Offset(-1.1852827482514838, -0.5029551986333607),
+    const Offset(-1.0253256532179804, -0.02034402043932526),
+    const Offset(-1.4488532714237397, 0.4948740308904742),
+    const Offset(-1.03142206223176, 0.81070400258819),
+    const Offset(-1.006747917852356, 1.3712062218039343),
+    const Offset(-0.5241429900291878, -1.2852518410112541),
+    const Offset(-0.8879593765104428, -0.9999680025850874),
+    const Offset(-0.9120835110799488, -0.4361605900585557),
+    const Offset(-0.8184877240407303, 1.1202520775469589),
+    const Offset(-0.15746058420492282, -1.1905035795387513),
+    const Offset(-0.11519948876183506, 1.3848147258237393),
+    const Offset(0.0035741796943844495, -1.3383908620447724),
+    const Offset(0.34408827443814394, 1.4514436242950461),
+    const Offset(0.709487222145941, -1.3468012918181573),
+    const Offset(0.6287522653614315, -0.8315879623940617),
+    const Offset(0.9716071801865485, 0.24311969613525442),
+    const Offset(0.7632982576031955, 0.8329765574976169),
+    const Offset(0.9923766847309081, 1.0592617071813715),
+    const Offset(1.2696730082820435, -1.0353385446957046),
+    const Offset(1.4266154921521208, -0.8382633931857755),
+    const Offset(1.298035226938996, -0.11544603567954526),
+    const Offset(1.4143230992455558, 0.10842501221141165),
+    const Offset(1.465352952354424, 0.6999947490821032),
+    const Offset(1.0462985816010146, 1.3874230508561505),
+    const Offset(100.0, -100.0),
+    const Offset(100.0, 100.0),
+  ],
+);

packages/flutter/test/painting/rounded_rectangle_border_test.dart

@@ -6,7 +6,7 @@ import 'package:flutter/painting.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 import '../rendering/mock_canvas.dart';
-import 'circle_border_test.dart';
+import 'common_matchers.dart';
 
 void main() {
   test('RoundedRectangleBorder', () {