Remove need to instantiate Platform and make methods static.

tools/testing/dart/test_runner.dart

Index: tools/testing/dart/test_runner.dart
diff --git a/tools/testing/dart/test_runner.dart b/tools/testing/dart/test_runner.dart
index dd857ea57bef1158f094d617f10dfbc407ec807b..caddb529b486cf200edf20fc93993e5711db83f7 100644
--- a/tools/testing/dart/test_runner.dart
+++ b/tools/testing/dart/test_runner.dart
@@ -254,7 +254,7 @@ class TestOutputImpl implements TestOutput {
   bool get unexpectedOutput() => !testCase.expectedOutcomes.contains(result);
 
   bool get hasCrashed() {
-    if (new Platform().operatingSystem() == 'windows') {
+    if (Platform.operatingSystem() == 'windows') {
       if (exitCode != 0) {
         // Suppress some flaky errors that crash the VM.
         // TODO(sigmund,efortuna): remove this when bug 2124 gets fixed.
@@ -292,7 +292,7 @@ class TestOutputImpl implements TestOutput {
   bool get hasFailed() {
     // TODO(efortuna): This is a total hack to keep our buildbots (more) green
     // while the VM team solves Issue 2124. Remove when issue is fixed.
-    if (new Platform().operatingSystem() == 'windows' && (exitCode == 253 ||
+    if (Platform.operatingSystem() == 'windows' && (exitCode == 253 ||
         exitCode == 3)) {
       for (String line in testCase.output.stdout) {
         if (line.startsWith('VM exited with signal 1073741819') ||
@@ -620,7 +620,7 @@ class RunningProcess {
 
   void runCommand(Command command,
                   void exitHandler(int exitCode)) {
-    if (new Platform().operatingSystem() == 'windows') {
+    if (Platform.operatingSystem() == 'windows') {
       // Windows can't handle the first command if it is a .bat file or the like
       // with the slashes going the other direction.
       // TODO(efortuna): Remove this when fixed (Issue 1306).
@@ -928,7 +928,7 @@ class ProcessQueue {
   String globalTemporaryDirectory() {
     if (_temporaryDirectory != null) return _temporaryDirectory;
 
-    if (new Platform().operatingSystem() == 'windows') {
+    if (Platform.operatingSystem() == 'windows') {
       throw new Exception(
           'Test suite requires temporary directory. Not supported on Windows.');
     }
@@ -981,7 +981,7 @@ class ProcessQueue {
    * True if we are using a browser + platform combination that needs the
    * Selenium server jar.
    */
-  bool get _needsSelenium() => new Platform().operatingSystem() == 'macos' &&
+  bool get _needsSelenium() => Platform.operatingSystem() == 'macos' &&
       browserUsed == 'safari';
 
   /** True if the Selenium Server is ready to be used. */
@@ -1004,7 +1004,7 @@ class ProcessQueue {
       // Check to see if the jar was already running before the program started.
       String cmd = 'ps';
       var arg = ['aux'];
-      if (new Platform().operatingSystem() == 'windows') {
+      if (Platform.operatingSystem() == 'windows') {
         cmd = 'tasklist';
         arg.add('/v');
       }
@@ -1064,7 +1064,7 @@ class ProcessQueue {
   void _startSeleniumServer() {
     // Get the absolute path to the Selenium jar.
     String filePath = new Options().script;
-    String pathSep = new Platform().pathSeparator();
+    String pathSep = Platform.pathSeparator();
     int index = filePath.lastIndexOf(pathSep);
     filePath = filePath.substring(0, index) + '${pathSep}testing${pathSep}';
     var dir = new Directory(filePath);