[Gin] Add V8IgnitionEager feature.

gin/gin_features.cc

Index: gin/gin_features.cc
diff --git a/gin/gin_features.cc b/gin/gin_features.cc
index 40de09d973a1d06cd3d1da29f6c5e033f8fabb74..38ccb541a12863948495858482affc96313f27a7 100644
--- a/gin/gin_features.cc
+++ b/gin/gin_features.cc
@@ -11,9 +11,16 @@ const base::Feature kV8Ignition {
   "V8Ignition", base::FEATURE_DISABLED_BY_DEFAULT
 };
 
-// Enables or disables lazy compilation for the V8 Ignition interpreter.
+// Enables lazy compilation for the V8 Ignition interpreter. Only
+// one of V8IgnitionLazy or V8IgnitionEager should be enabled.
 const base::Feature kV8IgnitionLazy {
   "V8IgnitionLazy", base::FEATURE_DISABLED_BY_DEFAULT
 };
 
+// Enables eager compilation for the V8 Ignition interpreter. Only
+// one of V8IgnitionLazy or V8IgnitionEager should be enabled.
+const base::Feature kV8IgnitionEager {
+  "V8IgnitionEager", base::FEATURE_DISABLED_BY_DEFAULT
+};
+
 }  // namespace features