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

gin/v8_initializer.cc

Index: gin/v8_initializer.cc
diff --git a/gin/v8_initializer.cc b/gin/v8_initializer.cc
index 4131f0481e93b71f63059ff053e5a0bf27f358fa..9f7e7013b44a94c91576e28a18134aa10a480a8a 100644
--- a/gin/v8_initializer.cc
+++ b/gin/v8_initializer.cc
@@ -367,7 +367,11 @@ void V8Initializer::Initialize(IsolateHolder::ScriptMode mode,
   }
 
   const char* ignition_enabled_crash_key = "N";
-  if (base::FeatureList::IsEnabled(features::kV8Future)) {
+  if (base::FeatureList::IsEnabled(features::kV8NoTurbo)) {
+    ignition_enabled_crash_key = "N";
+    std::string flag("--no-turbo");
+    v8::V8::SetFlagsFromString(flag.c_str(), static_cast<int>(flag.size()));
+  } else if (base::FeatureList::IsEnabled(features::kV8Future)) {
     ignition_enabled_crash_key = "Y";
     std::string flag("--future");
     v8::V8::SetFlagsFromString(flag.c_str(), static_cast<int>(flag.size()));