Implement important sites dialog for desktop.

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 5e8d2bd096ab997822ecbfa9b662def50992f9e4..c88588a4404f9677d8a452a798ed3ba939ff1474 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -161,6 +161,9 @@ const base::Feature kHappinessTrackingSystem {
     "HappinessTrackingSystem", base::FEATURE_DISABLED_BY_DEFAULT};
 #endif
 
+const base::Feature kImportantSitesInCbd{"ImportantSitesInCBD",
+                                         base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Controls whether the "improved recovery component" is used. The improved
 // recovery component is a redesigned Chrome component intended to restore
 // a broken Chrome updater in more scenarios than before.