This new frequency-based namer generally produces smaller output, which is great for deployment. It does however also result in different name allocations and thus “diffing” before/after the change will not produce useful outcomes. Furthermore, with the new scheme a small change in the Dart program might lead to major changes in the naming in the output. If output stability is more important than output size, you can still use the old namer. Simply use the option --no-frequency-based-minification when invoking dart2js.
We are making the new improved namer available on dev channel to get early feedback from you in time before the first release of 1.12 on the stable channel expected later this summer. Please give it a try and report any bugs you might find.
Posted by Stephan Herhut, Frequency-Based Minifier