Revert "Change dart:io Platform.script to return a Uri."

tests/standalone/coverage_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // This test forks a second vm process that runs the script tools/coverage.dart
 // and verifies that the coverage tool produces its expected output.
 // This test is mainly here to ensure that the coverage tool compiles and
 // runs.
 
 import "dart:async";
@@ skipping 34 matching lines @@
     print("Successfully matched all lines of '$targPath'");
   } else {
     print("Error: could not match all source code lines of '$targPath'");
     exit(-1);
   }
 }
 
 void main() {
   // Compute paths for coverage tool and coverage target relative
   // the the path of this script.
-  var scriptPath = dirname(Platform.script.toFilePath());
+  var scriptPath = dirname(Platform.script);
   var toolPath = normalize(join(scriptPath, coverageToolScript));
   targPath = normalize(join(scriptPath, coverageTargetScript));
 
   sourceLines = new File(targPath).readAsLinesSync();
   assert(sourceLines != null);
 
   var processOpts = [ "--compile_all", toolPath, targPath ];
 
   Process.start(Platform.executable, processOpts).then((Process process) {
     coverageToolProcess = process;
@@ skipping 13 matching lines @@
     futures.add(subscription.asFuture(true));
     subscription = stderrStringStream.listen(onCoverageOutput);
     futures.add(subscription.asFuture(true));
     futures.add(coverageToolProcess.exitCode.then(checkExitCode));
     Future.wait(futures).then((results) {
       checkSuccess();
       if (results.contains(false)) exit(-1);
     });
   });
 }