Update List constructor documentation, deprecate constructor.

Emphasize that the operation is going away,
and mark constructor as deprecated.

TEST= Refactoring+deprecation only, covered by existing tests.

Change-Id: I82aa044cd2cf7bf347b624371399f44bda8f4a07
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/173261
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Nate Bosch <nbosch@google.com>

pkg/testing/lib/src/test_dart/path.dart

@@ -121,7 +121,7 @@ class Path {
     while (common < length && pathSegments[common] == baseSegments[common]) {
       common++;
     }
-    final segments = new List<String>();
+    final segments = <String>[];
 
     if (common < baseSegments.length && baseSegments[common] == '..') {
       throw new ArgumentError("Invalid case of Path.relativeTo(base):\n"

pkg/testing/lib/src/test_dart/status_expression.dart

@@ -53,7 +53,7 @@ class Tokenizer {
   String expression;
   List<String> tokens;
 
-  Tokenizer(String this.expression) : tokens = new List<String>();
+  Tokenizer(String this.expression) : tokens = <String>[];
 
   // Tokens are : "(", ")", "$", ",", "&&", "||", "==", "!=", and (maximal) \w+.
   static final testRegexp =

pkg/testing/lib/src/test_dart/status_file_parser.dart

@@ -35,9 +35,9 @@ class Section {
 
   Section.always(this.statusFile, this.lineNumber)
       : condition = null,
-        testRules = new List<TestRule>();
+        testRules = <TestRule>[];
   Section(this.statusFile, this.condition, this.lineNumber)
-      : testRules = new List<TestRule>();
+      : testRules = <TestRule>[];
 
   bool isEnabled(Map<String, String> environment) =>
       condition == null || condition.evaluate(environment);
@@ -58,7 +58,7 @@ Future<TestExpectations> ReadTestExpectations(List<String> statusFilePaths,
 Future<void> ReadTestExpectationsInto(TestExpectations expectations,
     String statusFilePath, Map<String, String> environment) {
   var completer = new Completer();
-  List<Section> sections = new List<Section>();
+  List<Section> sections = <Section>[];
 
   void sectionsRead() {
     for (Section section in sections) {
@@ -233,7 +233,7 @@ class TestExpectations {
     _map.forEach((key, expectations) {
       if (_keyToRegExps[key] != null) return;
       var splitKey = key.split('/');
-      var regExps = new List<RegExp>(splitKey.length);
+      var regExps = new List<RegExp>.filled(splitKey.length, null);
       for (var i = 0; i < splitKey.length; i++) {
         var component = splitKey[i];
         var regExp = _regExpCache[component];