Adds UKM for autofill attributes in form_structure.

components/autofill/core/browser/autofill_metrics.h

Index: components/autofill/core/browser/autofill_metrics.h
diff --git a/components/autofill/core/browser/autofill_metrics.h b/components/autofill/core/browser/autofill_metrics.h
index 7fe9cc45353b7a975f878ab809b21ed616cc2a7d..15ee9a173c9debb9119f586cc6c5ce5773b62a2e 100644
--- a/components/autofill/core/browser/autofill_metrics.h
+++ b/components/autofill/core/browser/autofill_metrics.h
@@ -27,6 +27,8 @@ namespace internal {
 // Name constants are exposed here so they can be referenced from tests.
 extern const char kUKMCardUploadDecisionEntryName[];
 extern const char kUKMCardUploadDecisionMetricName[];
+extern const char kUKMDeveloperEngagementEntryName[];
+extern const char kUKMDeveloperEngagementMetricName[];
 }  // namespace internal
 
 namespace autofill {
@@ -84,12 +86,13 @@ class AutofillMetrics {
   };
 
   enum DeveloperEngagementMetric {
-    // Parsed a form that is potentially autofillable.
-    FILLABLE_FORM_PARSED = 0,
+    // Parsed a form that is potentially autofillable and does not contain any
+    // web developer-specified field type hint.
+    FILLABLE_FORM_PARSED_WITHOUT_TYPE_HINTS = 0,
     // Parsed a form that is potentially autofillable and contains at least one
     // web developer-specified field type hint, a la
     // http://is.gd/whatwg_autocomplete
-    FILLABLE_FORM_CONTAINS_TYPE_HINTS,
+    FILLABLE_FORM_PARSED_WITH_TYPE_HINTS,
     // Parsed a form that is potentially autofillable and contains at least one
     // UPI Virtual Payment Address hint (upi-vpa)
     FORM_CONTAINS_UPI_VPA_HINT,
@@ -700,6 +703,13 @@ class AutofillMetrics {
       const GURL& url,
       AutofillMetrics::CardUploadDecisionMetric upload_decision);
 
+  // Logs the developer engagement ukm for the specified |url| and autofill
+  // fields in the form structure.
+  static void LogDeveloperEngagementUkm(
+      ukm::UkmService* ukm_service,
+      const GURL& url,
+      AutofillMetrics::DeveloperEngagementMetric metric);
+
   // Logs the the |ukm_entry_name| with the specified |url| and the specified
   // |metrics|. Returns whether the ukm was sucessfully logged.
   static bool LogUkm(ukm::UkmService* ukm_service,