Change the behavior of open on files to not truncate by default

tools/testing/dart/test_suite.dart

Index: tools/testing/dart/test_suite.dart
diff --git a/tools/testing/dart/test_suite.dart b/tools/testing/dart/test_suite.dart
index bd7218e6669f531f43230aecc32106a8a434ff3b..ebdec8b3223f73127852510a85a9dd6b11aab245 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -358,13 +358,13 @@ class StandardTestSuite implements TestSuite {
       } else {
         dartLibraryFilename = 'test_as_library.dart';
         File file = new File('${tempDir.path}/$dartLibraryFilename');
-        RandomAccessFile dartLibrary = file.openSync(writable: true);
+        RandomAccessFile dartLibrary = file.openSync(FileMode.WRITE);
         dartLibrary.writeStringSync(WrapDartTestInLibrary(dartTestFilename));
         dartLibrary.closeSync();
       }
 
       File file = new File(dartWrapperFilename);
-      RandomAccessFile dartWrapper = file.openSync(writable: true);
+      RandomAccessFile dartWrapper = file.openSync(FileMode.WRITE);
       dartWrapper.writeStringSync(DartTestWrapper(
           'dart:dom',
           '../../../tests/isolate/src/TestFramework.dart',
@@ -375,7 +375,7 @@ class StandardTestSuite implements TestSuite {
     }
     // Create the HTML file for the test.
     File htmlTestBase = new File('${tempDir.path}/${getHtmlName(filename)}');
-    RandomAccessFile htmlTest = htmlTestBase.openSync(writable: true);
+    RandomAccessFile htmlTest = htmlTestBase.openSync(FileMode.WRITE);
     htmlTest.writeStringSync(GetHtmlContents(
         filename,
         '../../../client/testing/unittest/test_controller.js',
@@ -469,13 +469,13 @@ class StandardTestSuite implements TestSuite {
       } else {
         dartLibraryFilename = 'test_as_library.dart';
         File file = new File('${tempDir.path}/$dartLibraryFilename');
-        RandomAccessFile dartLibrary = file.openSync(writable: true);
+        RandomAccessFile dartLibrary = file.openSync(FileMode.WRITE);
         dartLibrary.writeStringSync(WrapDartTestInLibrary(testPath));
         dartLibrary.closeSync();
       }  
       
       File file = new File(dartWrapperFilename);
-      RandomAccessFile dartWrapper = file.openSync(writable: true);
+      RandomAccessFile dartWrapper = file.openSync(FileMode.WRITE);
       dartWrapper.writeStringSync(DartTestWrapper(
           domLibraryImport,
           '$dartDir/tests/isolate/src/TestFramework.dart',
@@ -486,7 +486,7 @@ class StandardTestSuite implements TestSuite {
     }
     // Create the HTML file for the test.
     File htmlTestBase = new File('${tempDir.path}/${getHtmlName(filename)}');
-    RandomAccessFile htmlTest = htmlTestBase.openSync(writable: true);
+    RandomAccessFile htmlTest = htmlTestBase.openSync(FileMode.WRITE);
     htmlTest.writeStringSync(GetHtmlContents(
         filename,
         '$dartDir/client/testing/unittest/test_controller.js',