Add buffering to _FileInputStream implementation.

tests/standalone/io/file_test.dart

 // Copyright (c) 2012, 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.
 //
 // Dart test program for testing file I/O.
 
 #import("dart:io");
 #import("dart:isolate");
 
 class MyListOfOneElement implements List {
@@ skipping 60 matching lines @@
   static void testReadWriteStream() {
     asyncTestStarted();
 
     // Read a file.
     String inFilename = getFilename("tests/vm/data/fixed_length_file");
     File file;
     InputStream input;
     int bytesRead;
 
     // Test reading all using readInto.
-    file = new File(inFilename);
-    input = file.openInputStream();
-    input.onData = () {
-      List<int> buffer1 = new List<int>(42);
-      bytesRead = input.readInto(buffer1, 0, 42);
+    var file1 = new File(inFilename);
+    var input1 = file1.openInputStream();
+    List<int> buffer1;
+    input1.onData = () {
+      buffer1 = new List<int>(42);
+      bytesRead = input1.readInto(buffer1, 0, 42);
       Expect.equals(42, bytesRead);
-      Expect.isTrue(input.closed);
+    };
+    input1.onError = (e) { throw e; };
+    input1.onClosed = () {
+      Expect.isTrue(input1.closed);
 
       // Test reading all using readInto and read.
-      file = new File(inFilename);
-      input = file.openInputStream();
-      input.onData = () {
-        bytesRead = input.readInto(buffer1, 0, 21);
+      var file2 = new File(inFilename);
+      var input2 = file2.openInputStream();
+      input2.onData = () {
+        bytesRead = input2.readInto(buffer1, 0, 21);
         Expect.equals(21, bytesRead);
-        buffer1 = input.read();
+        buffer1 = input2.read();
         Expect.equals(21, buffer1.length);
-        Expect.isTrue(input.closed);
+      };
+      input2.onError = (e) { throw e; };
+      input2.onClosed = () {
+        Expect.isTrue(input2.closed);
 
         // Test reading all using read and readInto.
-        file = new File(inFilename);
-        input = file.openInputStream();
-        input.onData = () {
-          buffer1 = input.read(21);
+        var file3 = new File(inFilename);
+        var input3 = file3.openInputStream();
+        input3.onData = () {
+          buffer1 = input3.read(21);
           Expect.equals(21, buffer1.length);
-          bytesRead = input.readInto(buffer1, 0, 21);
+          bytesRead = input3.readInto(buffer1, 0, 21);
           Expect.equals(21, bytesRead);
-          Expect.isTrue(input.closed);
+        };
+        input3.onError = (e) { throw e; };
+        input3.onClosed = () {
+          Expect.isTrue(input3.closed);
 
           // Test reading all using read.
-          file = new File(inFilename);
-          input = file.openInputStream();
-          input.onData = () {
-            buffer1 = input.read();
+          var file4 = new File(inFilename);
+          var input4 = file4.openInputStream();
+          input4.onData = () {
+            buffer1 = input4.read();
             Expect.equals(42, buffer1.length);
-            Expect.isTrue(input.closed);
+          };
+          input4.onError = (e) { throw e; };
+          input4.onClosed = () {
+            Expect.isTrue(input4.closed);
 
             // Write the contents of the file just read into another file.
             String outFilename =
                 tempDirectory.path.concat("/out_read_write_stream");
             file = new File(outFilename);
             OutputStream output = file.openOutputStream();
             bool writeDone = output.writeFrom(buffer1, 0, 42);
             Expect.equals(false, writeDone);
             output.onNoPendingWrites = () {
               output.close();
               output.onClosed = () {
                 // Now read the contents of the file just written.
                 List<int> buffer2 = new List<int>(42);
-                file = new File(outFilename);
-                input = file.openInputStream();
-                input.onData = () {
-                  bytesRead = input.readInto(buffer2, 0, 42);
+                var file6 = new File(outFilename);
+                var input6 = file6.openInputStream();
+                input6.onData = () {
+                  bytesRead = input6.readInto(buffer2, 0, 42);
                   Expect.equals(42, bytesRead);
                   // Now compare the two buffers to check if they are identical.
                   for (int i = 0; i < buffer1.length; i++) {
                     Expect.equals(buffer1[i],  buffer2[i]);
                   }
                 };
-                input.onClosed = () {
+                input6.onError = (e) { throw e; };
+                input6.onClosed = () {
                   // Delete the output file.
-                  file.deleteSync();
-                  Expect.isFalse(file.existsSync());
+                  file6.deleteSync();
+                  Expect.isFalse(file6.existsSync());
                   asyncTestDone("testReadWriteStream");
                 };
               };
             };
           };
         };
       };
     };
   }
 
@@ skipping 928 matching lines @@
       testWriteVariousLists();
       testDirectory();
       testDirectorySync();
     });
   }
 }
 
 main() {
   FileTest.testMain();
 }