v19.0 - 2021-09-02:
Tracing service and probes:
* Added ftrace clock reporting to the trace.
Trace Processor:
* Added support for longs/doubles to RUN_METRIC.
* Added power profile data for sunfish, redfin, and bramble.
* Added experimental Python library for computing slice breakdowns.
* Fixed parsing of JSON escape sequences.
* Fixed JSON trace detection.
UI:
* Added local cacheing of traces. Traces are reloaded in case of refresh or
tab being discarded by the browser.
* Added icon to distinguish metric-derived tracks.
* Added release channel selector to feature flags page.
* Fixed crash with null slice names.
SDK:
* Added some missing NESTABLE_ASYNC legacy trace macros.
* Fixed reporting of producer uid in --query.
* Fixed version numbering scheme for minor versions. Previously versions
were numbered as like v19.0.42 where 42 represented the number of commits
since the last major version release. This was ambiguous in the presence
of branches. Now versions are numbered like v19.0-ab12cd34 where ab12cd34
is the shortened Git commit-ish.
