Log Form/Field Signature hashes

This CL introduces the logging for form and field signature hashes as
they exist in UKMs to simplify detecting a specific form and field.

R=kolos@chromium.org

Bug: 928595
Change-Id: I5a5f3a9311896e8d9ec9b46d3862e0182dbb5aa5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1733546Reviewed-by: Maxim Kolosovskiy <kolos@chromium.org>
Commit-Queue: Dominic Battré <battre@chromium.org>
Auto-Submit: Dominic Battré <battre@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685244}

components/autofill/core/browser/autofill_metrics.cc

@@ -82,18 +82,16 @@ std::string PreviousSaveCreditCardPromptUserDecisionToString(
   return previous_response;
 }
 
-// Reduce FormSignature space (in UKM) to a small range for privacy reasons.
+}  // namespace
+
 int64_t HashFormSignature(autofill::FormSignature form_signature) {
   return static_cast<uint64_t>(form_signature) % 1021;
 }
 
-// Reduce FieldSignature space (in UKM) to a small range for privacy reasons.
 int64_t HashFieldSignature(autofill::FieldSignature field_signature) {
   return static_cast<uint64_t>(field_signature) % 1021;
 }
 
-}  // namespace
-
 // First, translates |field_type| to the corresponding logical |group| from
 // |FieldTypeGroupForMetrics|.  Then, interpolates this with the given |metric|,
 // which should be in the range [0, |num_possible_metrics|).

components/autofill/core/browser/autofill_metrics.h

@@ -35,6 +35,12 @@ class CreditCard;
 // A given maximum is enforced to minimize the number of buckets generated.
 extern const int kMaxBucketsCount;
 
+// Reduce FormSignature space (in UKM) to a small range for privacy reasons.
+int64_t HashFormSignature(autofill::FormSignature form_signature);
+
+// Reduce FieldSignature space (in UKM) to a small range for privacy reasons.
+int64_t HashFieldSignature(autofill::FieldSignature field_signature);
+
 class AutofillMetrics {
  public:
   enum AutofillProfileAction {

components/autofill/core/browser/form_structure.cc

@@ -2188,7 +2188,10 @@ void FormStructure::RationalizeTypeRelationships() {
 LogBuffer& operator<<(LogBuffer& buffer, const FormStructure& form) {
   buffer << Tag{"div"} << Attrib{"class", "form"};
   buffer << Tag{"table"};
-  buffer << Tr{} << "Form signature:" << form.form_signature();
+  buffer << Tr{} << "Form signature:"
+         << base::StrCat({base::NumberToString(form.form_signature()), " - ",
+                          base::NumberToString(
+                              HashFormSignature(form.form_signature()))});
   buffer << Tr{} << "Form name:" << form.form_name();
   buffer << Tr{} << "Target URL:" << form.target_url();
   for (size_t i = 0; i < form.field_count(); ++i) {
@@ -2197,7 +2200,11 @@ LogBuffer& operator<<(LogBuffer& buffer, const FormStructure& form) {
     const AutofillField* field = form.field(i);
     buffer << Tag{"td"};
     buffer << Tag{"table"};
-    buffer << Tr{} << "Signature:" << field->GetFieldSignature();
+    buffer << Tr{} << "Signature:"
+           << base::StrCat(
+                  {base::NumberToString(field->GetFieldSignature()), " - ",
+                   base::NumberToString(
+                       HashFieldSignature(field->GetFieldSignature()))});
     buffer << Tr{} << "Name:" << field->parseable_name();
 
     auto type = field->Type().ToString();