Add a Finch feature and runtime flag for multidevice.

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 99098ff75725445b2d5e41c4478876e613f2d5aa..1b66b3452b24db8541893e804fdd8011b5b68c53 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -252,6 +252,12 @@ const base::Feature kModuleDatabase{"ModuleDatabase",
                                     base::FEATURE_DISABLED_BY_DEFAULT};
 #endif
 
+#if defined(OS_CHROMEOS)
+// Enables or disables multidevice features and corresponding UI on Chrome OS.
+const base::Feature kMultidevice{"Multidevice",
+                                 base::FEATURE_DISABLED_BY_DEFAULT};
+#endif
+
 // Enables the use of native notification centers instead of using the Message
 // Center for displaying the toasts.
 #if BUILDFLAG(ENABLE_NATIVE_NOTIFICATIONS)