Bug 1063857 - Fix reftests for new justification algorithm.

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rename : layout/reftests/bugs/503399-ref.html => layout/base/tests/bug503399-ref.html
rename : layout/reftests/bugs/503399.html => layout/base/tests/bug503399.html
Bug 1063857 - Improve selecting on justified characters. r=roc
Bug 1063857 - Implement new justification algorithm. r=roc,masayuki