Normalize incoming AssetID paths.

pkg/pkg.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.
 
 # Don't run any test-like files that show up in packages directories. It
 # shouldn't be necessary to run "pub install" in these packages, but if you do
 # it shouldn't break the tests.
 */packages/*/*: Skip
 */*/packages/*/*: Skip
 */*/*/packages/*/*: Skip
@@ skipping 56 matching lines @@
 # Skip browser-specific tests on VM
 [ $runtime == vm ]
 path/test/browser_test: Fail, OK # Uses dart:html
 intl/test/find_default_locale_browser_test: Skip
 intl/test/date_time_format_http_request_test: Skip
 
 [ $runtime == vm && $system == windows ]
 docgen/test/single_library_test: Fail # Issue 11985
 intl/test/find_default_locale_standalone_test: Fail # Issue 8110
 intl/test/message_extraction/message_extraction_test: Fail # Issue 9167
-polymer/test/transform/import_inliner_test: Fail # Issue 12622
 
 [ $compiler == dart2js ]
 stack_trace/test/trace_test: Pass, Timeout # Issue 11645
 
 [ $compiler == dartanalyzer || $compiler == dart2analyzer]
 # These tests are runtime negative but statically positive, so we skip
 # them in the analyzer.
 unittest/test/mock_regexp_negative_test: Skip
 unittest/test/mock_stepwise_negative_test: Skip
 
@@ skipping 116 matching lines @@
 # Skip tests on the VM if the package depends on dart:html
 [ $runtime == vm ]
 custom_element: Skip
 mdv: Skip
 mutation_observer: Skip
 polymer_expressions/test/syntax_test: Skip
 third_party/html5lib/test/browser/browser_test: Skip
 
 [ $runtime == safari || $runtime == chrome || $runtime == ie9 || $runtime == ff || $runtime == dartium || $runtime == drt ]
 docgen/test/single_library_test: Skip # Uses dart:io