Add readAsStringSync() to File.

pkg/analyzer/test/file_system/physical_resource_provider_test.dart

Index: pkg/analyzer/test/file_system/physical_resource_provider_test.dart
diff --git a/pkg/analyzer/test/file_system/physical_resource_provider_test.dart b/pkg/analyzer/test/file_system/physical_resource_provider_test.dart
index 02eb20694c9afe5846abde536108c2c2f455e3f7..33ef8767ebda7534a5046a2ceeb01c87e307d182 100644
--- a/pkg/analyzer/test/file_system/physical_resource_provider_test.dart
+++ b/pkg/analyzer/test/file_system/physical_resource_provider_test.dart
@@ -102,6 +102,19 @@ class FileTest extends _BaseTest {
     expect(parent.path, equals(tempPath));
   }
 
+  void test_readAsStringSync_doesNotExist() {
+    File file = PhysicalResourceProvider.INSTANCE.getResource(path);
+    expect(() {
+      file.readAsStringSync();
+    }, throwsA(_isFileSystemException));
+  }
+
+  void test_readAsStringSync_exists() {
+    new io.File(path).writeAsStringSync('abc');
+    File file = PhysicalResourceProvider.INSTANCE.getResource(path);
+    expect(file.readAsStringSync(), 'abc');
+  }
+
   void test_shortName() {
     expect(file.shortName, 'file.txt');
   }