Bug 888086 - Use StringBuilder in sync/Utils.java
Bug 888086 - Review comment: Space between arithmetic operators.
Bug 888086 - Followup: Add final keyword.
Bug 888086 - Part 2: Add byte2hex test.
Bug 888086 - Followup: byte2hex -> byte2Hex for consistency.
Bug 888086 - Followup: Move arrays to class constants.
Bug 888086 - Followup: Add testHex2Byte.
Bug 888086 - Review comment: Add hex2Byte roundtrip tests.
Bug 888086 - Use StringBuilder in sync/Utils.java. r=rnewman