Backwards Incompatible Changes

• Add the ability to center a dialog inside a parent parent element. (eaf55f3db6fea3d14293f6fea3c9805e4f678567)

Other Changes

• Makes closure/html types' constructors private (f3db3e6e2e998d3e52f681ee4ca91ffa38487085)
• Deprecate setObjectData (211bb6524c96b1b8ca9d156ec12811eb3406c308) and setFrameSrc (1763bed09dc1007bf05485f974af12588b4611c9) in SafeHtml
• Add a way to check if Html5History is using the fragment for the token. (a6fa5b05b2d305f71a7b9adf720e1c1dc8a116b6)