Add Ignition to about:flags.

chrome/common/chrome_features.cc

Index: chrome/common/chrome_features.cc
diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
index e1c558bcde2c91b16cc46409eb3732333673bb01..51d1b1fd63ddce338f593d7e6b2f090d3cb26f14 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -27,6 +27,11 @@ const base::Feature kMaterialDesignHistoryFeature {
   "MaterialDesignHistory", base::FEATURE_DISABLED_BY_DEFAULT
 };
 
+// Enables or disables the experimental V8 Ignition interpreter.
+const base::Feature kV8Ignition {
+  "V8Ignition", base::FEATURE_DISABLED_BY_DEFAULT
+};
+
 #if defined(OS_CHROMEOS)
 // Runtime flag that indicates whether this leak detector should be enabled in
 // the current instance of Chrome.