[Gin] Add V8NoTurbo experiment to disable Ignition+TurboFan.

gin/gin_features.cc

Index: gin/gin_features.cc
diff --git a/gin/gin_features.cc b/gin/gin_features.cc
index 7699db7a2869118410178eca3b0d3039194980c8..e6fe5ae1cca6f7a245ade7f56f89bf2869a01254 100644
--- a/gin/gin_features.cc
+++ b/gin/gin_features.cc
@@ -6,12 +6,15 @@
 
 namespace features {
 
-// Enables or disables the future compiler pipeline of V8, with the Ignition
-// interpreter and TurboFan compiler.
+// Enables future experimental features of V8.
 const base::Feature kV8Future {
   "V8Future", base::FEATURE_DISABLED_BY_DEFAULT
 };
 
+// Disables the new compiler pipeline of V8, with the Ignition interpreter and
+// TurboFan compiler.
+const base::Feature kV8NoTurbo{"V8NoTurbo", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables or disables the V8 Ignition interpreter on low end
 // Android devices.
 const base::Feature kV8IgnitionLowEnd {