v18.0 - 2021-08-02:
Tracing service and probes:
* Added cross-compiler toolchains for Linux-{arm,64} based on Debian Sid.
These will be used for generating monthly releases' prebuilts via LUCI.
Trace Processor:
* Added 'android_gpu' metric to report residency information for each GPU
frequency (via `trace_processor_shell --run-metrics android_gpu`).
* Removed the RawQuery RPC interface.
UI:
* Added a highlighted section to thread slices to visualize CPU time
(darker) verses wall time (lighter).
* Added global counter tracks for perf counters (e.g. "CPU 0 cycles", "CPU 0
instructions") when the 'linux.perf' data source (traced_perf) is used.
* Added a (feature) 'Flags' page to enable/disable individual metrics.
* Fixed races that could cause occasional crashes when loading a trace
from a permalink.
SDK:
* Fix undefined reference on ~TracingMuxerFake when building the SDK.
