Add a flag for the password manager force-saving experiment.

components/password_manager/core/common/experiments.h

Index: components/password_manager/core/common/experiments.h
diff --git a/components/password_manager/core/common/experiments.h b/components/password_manager/core/common/experiments.h
index 49c0745537c9ea0da9b1057ab733578853fe88b3..d708a81910ccc14039d413761268cc19d374d4b2 100644
--- a/components/password_manager/core/common/experiments.h
+++ b/components/password_manager/core/common/experiments.h
@@ -11,6 +11,9 @@ namespace password_manager {
 // settings.
 bool ManageAccountLinkExperimentEnabled();
 
+// True iff the force-saving of passwords is enabled.
+bool ForceSavingExperimentEnabled();
+
 }  // namespace password_manager
 
 #endif  // COMPONENTS_PASSWORD_MANAGER_CORE_COMMON_EXPERIMENTS_H_