Revert "Make changes to test.dart and frogsh for Windows."

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 c11cb0ea2661d383d04897bb281dc85803a5d758..8acf632e86aa4a28988bf37697beb0a47962597f 100644
--- a/tools/testing/dart/test_runner.dart
+++ b/tools/testing/dart/test_runner.dart
@@ -243,12 +243,6 @@ class RunningProcess {
   void runCommand(String executable,
                   List<String> arguments,
                   void exitHandler(int exitCode)) {
-    if (new 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).
-      executable = executable.replaceAll('/', '\\');
-    }
     process = new Process.start(executable, arguments);
     process.exitHandler = exitHandler;
     startTime = new Date.now();