Add Timer implementation for dart2js. Also moves tests to appropriate location.

tests/standalone/standalone.status

 # 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.
 
 out_of_memory_test: Skip # Issue 2345
 
 package/invalid_uri_test: Fail, OK # Fails intentionally
 
 [ $runtime == vm && $checked ]
 # These tests have type errors on purpose.
@@ skipping 39 matching lines @@
 
 [ $arch == arm ]
 *: Skip
 
 
 [ $arch == simarm ]
 *: Skip
 
 [ $compiler == dart2js ]
 medium_integer_test: Fail, OK # cannot resolve type Mint
-io/timer_cancel_test: Fail # Needs Timer to run.
-io/timer_cancel1_test: Fail # Needs Timer to run.
-io/timer_cancel2_test: Fail # Needs Timer to run.
-io/multiple_timer_test: Fail # Needs Timer to run.
-io/timer_test: Fail # Needs Timer to run.
-io/timer_repeat_test: Fail # Needs Timer to run.
 
 [ $compiler == dart2js && $runtime == d8 ]
 assert_test: Fail # Assert not implemented
 byte_array_test: Fail, OK # ByteArray
 deoptimization_test: Fail, OK # Requires bigint.
 out_of_memory_test: Fail, OK # d8 handles much larger arrays than Dart VM.
 io/http_parser_test: Fail, OK # ByteArray
 io/options_test: Fail, OK # Cannot pass options to d8.
 
 [ $compiler == dart2js && $runtime == none ]
 io/options_test: Fail
 
 [$compiler == dart2js && $browser ]
 *: Skip
 
 [$compiler == dart2js && $checked ]
 io/http_read_test: Skip # Timeout TODO(ngeoffray): investigate
 io/list_input_stream_test: Skip # Timeout TODO(ngeoffray): investigate
 
 [ $compiler == dart2dart ]
 # Skip until we stabilize language tests.
 *: Skip