Add a flag to enable tracing to systrace. (#27208)

diff --git a/packages/flutter_tools/lib/src/device.dart b/packages/flutter_tools/lib/src/device.dart
index 94030fe..9d46ffe 100644
--- a/packages/flutter_tools/lib/src/device.dart
+++ b/packages/flutter_tools/lib/src/device.dart
@@ -356,6 +356,7 @@
     this.enableSoftwareRendering = false,
     this.skiaDeterministicRendering = false,
     this.traceSkia = false,
+    this.traceSystrace = false,
     this.useTestFonts = false,
     this.observatoryPort,
    }) : debuggingEnabled = true;
@@ -367,6 +368,7 @@
     enableSoftwareRendering = false,
     skiaDeterministicRendering = false,
     traceSkia = false,
+    traceSystrace = false,
     observatoryPort = null;
 
   final bool debuggingEnabled;
@@ -376,6 +378,7 @@
   final bool enableSoftwareRendering;
   final bool skiaDeterministicRendering;
   final bool traceSkia;
+  final bool traceSystrace;
   final bool useTestFonts;
   final int observatoryPort;