[Autofill] Introduce kAutofillAddressProfileSavePrompt feature

This CL introduces a feature toggle than controls showing explicit save
prompts before storing address profiles.

Bug: 1135178
Change-Id: If72c323489a7cee20ea9d812ba8945b4dfe2e366
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2450094
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Reviewed-by: Matthias Körber <koerber@google.com>
Cr-Commit-Position: refs/heads/master@{#813805}

components/autofill/core/common/autofill_features.cc

@@ -24,6 +24,13 @@ namespace features {
 const base::Feature kAutofillAddressEnhancementVotes{
     "kAutofillAddressEnhancementVotes", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// TODO(crbug.com/1135188): Remove this feature flag after the explicit save
+// prompts for address profiles is complete.
+// When enabled, a save prompt will be shown to user upon form submission before
+// storing any detected address profile.
+const base::Feature kAutofillAddressProfileSavePrompt{
+    "kAutofillAddressProfileSavePrompt", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // By default, AutofillAgent and, if |kAutofillProbableFormSubmissionInBrowser|
 // is enabled, also ContentAutofillDriver omit duplicate form submissions, even
 // though the form's data may have changed substantially. If enabled, the

components/autofill/core/common/autofill_features.h

@@ -22,6 +22,7 @@ namespace features {
 
 // All features in alphabetical order.
 extern const base::Feature kAutofillAddressEnhancementVotes;
+extern const base::Feature kAutofillAddressProfileSavePrompt;
 extern const base::Feature kAutofillAllowDuplicateFormSubmissions;
 extern const base::Feature kAutofillAllowHtmlTypeCountryCodesWithFullNames;
 extern const base::Feature kAutofillAllowNonHttpActivation;