Remove redundant set of ResolvableLibrary.libraryElement.
Remove redundant set of ResolvableLibrary.libraryElement.

LibraryElementBuilder.buildLibrary2() always sets it, so there's no
reason for the caller to set it as well.

R=brianwilkerson@google.com

Review URL: https://codereview.chromium.org//839463003

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@42798 260f80e4-7a28-3924-810f-c04153c831b5

dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk