Change fill-on-account-select to use Features API, not a custom flag

components/autofill/core/common/autofill_switches.cc

Index: components/autofill/core/common/autofill_switches.cc
diff --git a/components/autofill/core/common/autofill_switches.cc b/components/autofill/core/common/autofill_switches.cc
index b553a9577054722cc5f0cf8833c31890d14a8b59..42276f839329bbf75a0a4b2b38c726a13b0e2ad7 100644
--- a/components/autofill/core/common/autofill_switches.cc
+++ b/components/autofill/core/common/autofill_switches.cc
@@ -12,10 +12,6 @@ namespace switches {
 // credit card form.
 const char kDisableCreditCardScan[]         = "disable-credit-card-scan";
 
-// Disables the experiment for the password manager to only fill on account
-// selection, rather than autofilling on page load.
-const char kDisableFillOnAccountSelect[]    = "disable-fill-on-account-select";
-
 // Disables the experimental Full Form Autofill on iOS feature.
 const char kDisableFullFormAutofillIOS[]    = "disable-full-form-autofill-ios";
 
@@ -40,10 +36,6 @@ const char kDisableSingleClickAutofill[]    = "disable-single-click-autofill";
 // credit card form.
 const char kEnableCreditCardScan[]          = "enable-credit-card-scan";
 
-// Enables the experiment for the password manager to only fill on account
-// selection, rather than autofilling on page load, with highlighting of fields.
-const char kEnableFillOnAccountSelect[]     = "enable-fill-on-account-select";
-
 // Enables the experimental Full Form Autofill on iOS feature.
 const char kEnableFullFormAutofillIOS[]     = "enable-full-form-autofill-ios";