fixed front end test, moved tests to abstract away color.tostring

Author: gaaclarke

flutter_frontend_server/test/to_string_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:io' as io;
+import 'dart:ui' show Color;
 
 import 'package:engine_repo_tools/engine_repo_tools.dart';
 import 'package:path/path.dart' as path;
@@ -60,7 +61,7 @@ void main() {
     ]));
     final runResult = io.Process.runSync(dart, <String>[regularDill]);
     checkProcessResult(runResult);
-    var paintString = '"Paint.toString":"Paint(Color(0xffffffff))"';
+    var paintString = '"Paint.toString":"Paint(${const Color(0xffffffff)})"';
     if (buildDir.contains('release')) {
       paintString = '"Paint.toString":"Instance of \'Paint\'"';
     }

testing/dart/image_filter_test.dart

@@ -293,7 +293,7 @@ void main() async {
       ).toString(),
       contains(
         'matrix([10.0, 0.0, 0.0, 0.0, 0.0, 10.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, -0.0, -0.0, 0.0, 1.0], FilterQuality.low) -> '
-        'ColorFilter.mode(Color(alpha: 1.0000, red: 0.6706, green: 0.8039, blue: 0.9373, colorSpace: ColorSpace.sRGB), BlendMode.color) -> '
+        'ColorFilter.mode(${const Color(0xFFABCDEF)}, BlendMode.color) -> '
         'blur(20.0, 20.0, repeated) -> '
         'blur(30.0, 30.0, mirror)'
       ),

testing/dart/text_test.dart

@@ -80,7 +80,7 @@ void testTextStyle() {
     );
     expect(
       ts1.toString(),
-      equals('TextStyle(color: Color(alpha: 1.0000, red: 0.0000, green: 1.0000, blue: 0.0000, colorSpace: ColorSpace.sRGB), decoration: unspecified, decorationColor: unspecified, decorationStyle: unspecified, decorationThickness: unspecified, fontWeight: FontWeight.w800, fontStyle: unspecified, textBaseline: unspecified, fontFamily: unspecified, fontFamilyFallback: unspecified, fontSize: 10.0, letterSpacing: unspecified, wordSpacing: unspecified, height: 100.0x, leadingDistribution: unspecified, locale: unspecified, background: unspecified, foreground: unspecified, shadows: unspecified, fontFeatures: unspecified, fontVariations: unspecified)'),
+      equals('TextStyle(color: ${const Color(0xFF00FF00)}, decoration: unspecified, decorationColor: unspecified, decorationStyle: unspecified, decorationThickness: unspecified, fontWeight: FontWeight.w800, fontStyle: unspecified, textBaseline: unspecified, fontFamily: unspecified, fontFamilyFallback: unspecified, fontSize: 10.0, letterSpacing: unspecified, wordSpacing: unspecified, height: 100.0x, leadingDistribution: unspecified, locale: unspecified, background: unspecified, foreground: unspecified, shadows: unspecified, fontFeatures: unspecified, fontVariations: unspecified)'),
     );
     expect(
       ts2.toString(),