Migrate *-ime-thread switches to feature API

content/public/common/content_features.cc

Index: content/public/common/content_features.cc
diff --git a/content/public/common/content_features.cc b/content/public/common/content_features.cc
index 5b3bf32d81643a73052c4347fa7692099efe1502..02ad1f2b6901658bbcc26283184b38b3a1660a83 100644
--- a/content/public/common/content_features.cc
+++ b/content/public/common/content_features.cc
@@ -64,6 +64,11 @@ const base::Feature kWebFontsIntervention{"WebFontsIntervention",
                                           base::FEATURE_DISABLED_BY_DEFAULT};
 
 #if defined(OS_ANDROID)
+// Use IME's own thread instead of using main UI thread. It also means that
+// we will not use replica editor and do a round trip to renderer to synchronize
+// with Blink data.
+const base::Feature kImeThread{"ImeThread", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // FeatureList definition for the Seccomp field trial.
 const base::Feature kSeccompSandboxAndroid{"SeccompSandboxAndroid",
                                            base::FEATURE_DISABLED_BY_DEFAULT};