Merge the dart:uri library into dart:core and update the Uri class

tests/standalone/standalone.status

 # 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.
 
 package/invalid_uri_test: Fail, OK # Fails intentionally
 
 [ $runtime == vm ]
 # Fails because checked-in dart executable is not up to date.
 io/test_runner_test: Fail
 # Fails because checked-in dart executable is not up to date.
@@ skipping 86 matching lines @@
 byte_array_view_optimized_test: Skip # dart:typed_data support needed.
 io/web_socket_protocol_processor_test: Skip  # Importing code with external keyword
 io/url_encoding_test: Skip  # Importing code with external keyword
 int_array_load_elimination_test: Skip  # This is a VM test
 medium_integer_test: Fail, OK # Test fails with JS number semantics: issue 1533.
 io/process_exit_negative_test: Fail, OK # relies on a static error that is a warning now.
 package/package_isolate_test: Skip # spawnUri does not work in dart2js. See issue 3051
 debugger/*: Skip # Do not run standalone vm debugger tests with dart2js.
 left_shift_bit_and_op_test: Skip # Integers exceed dart2js precision.
 pow_test: Skip # Precision > 53 bits.
+io/test_runner_test: Fail # Library dart:uri removed.
+io/skipping_dart2js_compilations_test: Skip # Library dart:uri removed.
 
 [ $compiler == dart2js && $jscl ]
 assert_test: Fail, OK # Assumes unspecified fields on the AssertionError.
 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/options_test: Fail, OK # Cannot pass options to d8.
 io/http_parser_test: Fail, OK # Cancelling a Timer not implemented in d8/jsshell.
 
 [ $compiler == dart2js && $runtime == none ]
@@ skipping 15 matching lines @@
 *: Skip
 
 [ $arch == simarm ]
 *: Skip
 
 [ $arch == mips ]
 *: Skip
 
 [ $arch == simmips ]
 *: Skip