[flutter_runner] Enable Skia tracing by default on Fuchsia (#13457)
[flutter_runner] Enable Skia tracing by default on Fuchsia (#13457)

Since Flutter tracing is wired up to Fuchsia system level tracing (and
that includes Skia tracing within Flutter), it makes more sense to
enable Skia tracing by default on Fuchsia, and to control Flutter Skia
tracing, rely on whether Fuchsia system tracing is enabled, in progress,
and contains the "skia" category.
cdotstout/sky_engine,jason-simmons/flutter_engine,jamesr/sky_engine,devoncarew/sky_engine,jamesr/flutter_engine,Hixie/sky_engine,jamesr/flutter_engine,cdotstout/sky_engine,cdotstout/sky_engine,chinmaygarde/sky_engine,chinmaygarde/flutter_engine,devoncarew/engine,Hixie/sky_engine,mikejurka/engine,jason-simmons/sky_engine,devoncarew/engine,Hixie/sky_engine,devoncarew/sky_engine,devoncarew/sky_engine,jason-simmons/flutter_engine,jason-simmons/sky_engine,jason-simmons/flutter_engine,jason-simmons/sky_engine,jamesr/sky_engine,cdotstout/sky_engine,tvolkert/engine,chinmaygarde/sky_engine,jason-simmons/flutter_engine,devoncarew/sky_engine,aam/engine,rmacnak-google/engine,jamesr/sky_engine,tvolkert/engine,mikejurka/engine,rmacnak-google/engine,mikejurka/engine,jamesr/flutter_engine,jason-simmons/sky_engine,chinmaygarde/sky_engine,mikejurka/engine,devoncarew/sky_engine,aam/engine,cdotstout/sky_engine,jason-simmons/flutter_engine,flutter/engine,devoncarew/engine,chinmaygarde/sky_engine,cdotstout/sky_engine,devoncarew/engine,Hixie/sky_engine,flutter/engine,chinmaygarde/sky_engine,aam/engine,jamesr/flutter_engine,jamesr/flutter_engine,jamesr/sky_engine,rmacnak-google/engine,tvolkert/engine,jason-simmons/flutter_engine,mikejurka/engine,Hixie/sky_engine,flutter/engine,devoncarew/engine,chinmaygarde/sky_engine,aam/engine,aam/engine,devoncarew/engine,aam/engine,chinmaygarde/flutter_engine,flutter/engine,mikejurka/engine,chinmaygarde/flutter_engine,chinmaygarde/sky_engine,Hixie/sky_engine,mikejurka/engine,flutter/engine,aam/engine,tvolkert/engine,jamesr/flutter_engine,jamesr/sky_engine,jason-simmons/flutter_engine,chinmaygarde/flutter_engine,cdotstout/sky_engine,aam/engine,jamesr/flutter_engine,rmacnak-google/engine,chinmaygarde/flutter_engine,rmacnak-google/engine,chinmaygarde/flutter_engine,Hixie/sky_engine,jamesr/flutter_engine,rmacnak-google/engine,mikejurka/engine,jason-simmons/sky_engine,rmacnak-google/engine,Hixie/sky_engine,jason-simmons/sky_engine,flutter/engine,tvolkert/engine,mikejurka/engine,jamesr/flutter_engine,tvolkert/engine,devoncarew/sky_engine,jamesr/sky_engine,jason-simmons/flutter_engine,devoncarew/engine,jamesr/sky_engine,flutter/engine,tvolkert/engine,devoncarew/sky_engine,jason-simmons/sky_engine,chinmaygarde/flutter_engine,flutter/engine