Release 2.2.2

Features

• Some performance improvements to line charts (#3524)
• Performance improvements in the Text plugin due to batch HTML
  sanitization (#3529)
• Performance improvements in backend markdown cleaning for tag
  rendering (#3599)
• CSS/layout performance optimization by applying layout/layer bound where
  possible (#3642)
• The tensorboard dev list subcommand now reports the total size of stored
  tensors (used as the backing storage type for Histograms) (#3652)

TensorBoard.dev updates

• TensorBoard.dev now supports the Histograms plugin, for experiments
  uploaded starting from this release
  • The tensorboard dev upload subcommand now sends the histograms, when
    available, so that it can be rendered via the Histograms plugin on
    TensorBoard.dev
• This release may support additional plugins in the future, once those plugins
  are enabled in the TensorBoard.dev service

Breaking changes

• The experimental and legacy SQLite support (via the --db_import and --db
  flags) is removed to ease maintenance (#3539)