dart2js crashes when .packages contains same package name twice

[harryterkelsen]

stdout:

The compiler crashed: FormatException: Same package name occured twice. (at offset 56)
#0      parse (package:package_config/packages_file.dart:66:7)
#1      Compiler.setupPackages.<anonymous closure> (file:///usr/local/google/home/het/code/dart/sdk/pkg/compiler/lib/src/apiimpl.dart:403:29)
#2      _RootZone.runUnary (dart:async/zone.dart:1165)
#3      _Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:502)
#4      _Future._propagateToListeners (dart:async/future_impl.dart:585)
#5      _Future._completeWithValue (dart:async/future_impl.dart:376)
#6      _Future._asyncComplete.<anonymous closure> (dart:async/future_impl.dart:430)
#7      _microtaskLoop (dart:async/schedule_microtask.dart:43)
#8      _microtaskLoopEntry (dart:async/schedule_microtask.dart:52)
#9      _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:96)
#10     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:149)