[Autofill] Add FormEvent logging for "will submit form".

components/autofill/core/browser/autofill_metrics.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_AUTOFILL_CORE_BROWSER_AUTOFILL_METRICS_H_
 #define COMPONENTS_AUTOFILL_CORE_BROWSER_AUTOFILL_METRICS_H_
 
 #include <stddef.h>
 #include <string>
 
@@ skipping 251 matching lines @@
     // to fill.
     FORM_EVENT_SERVER_SUGGESTION_FILLED,
     // A masked server card suggestion was used to fill the form.
     FORM_EVENT_MASKED_SERVER_CARD_SUGGESTION_FILLED,
     // A suggestion was used to fill the form. The origin type (local or server
     // or masked server card) of the first selected within a page load will
     // determine which of the following two will be fired.
     FORM_EVENT_LOCAL_SUGGESTION_FILLED_ONCE,
     FORM_EVENT_SERVER_SUGGESTION_FILLED_ONCE,
     FORM_EVENT_MASKED_SERVER_CARD_SUGGESTION_FILLED_ONCE,
+    // An autofillable form is about to be submitted. If the submission is not
+    // interrupted by JavaScript, the "form submitted" events below will also be
+    // logged.
+    FORM_EVENT_WILL_SUBMIT,

[Ilya Sherman, 2015/03/18 22:42:10]

Why are you adding this event in the middle of the list?  I believe that this
enumeration backs an enumerated UMA histogram, right?

[Mathieu, 2015/03/23 15:24:02]

Done. Yes of course.

     // A form was submitted. Depending on the user filling a local, server,
     // masked server card or no suggestion one of the following will be
     // triggered. Only one of the following four will be triggered per page
     // load.
     FORM_EVENT_NO_SUGGESTION_SUBMITTED_ONCE,
     FORM_EVENT_LOCAL_SUGGESTION_SUBMITTED_ONCE,
     FORM_EVENT_SERVER_SUGGESTION_SUBMITTED_ONCE,
     FORM_EVENT_MASKED_SERVER_CARD_SUGGESTION_SUBMITTED_ONCE,
     // A masked server card suggestion was selected to fill the form.
     FORM_EVENT_MASKED_SERVER_CARD_SUGGESTION_SELECTED,
     // Same as above but only triggered once per page load.
     FORM_EVENT_MASKED_SERVER_CARD_SUGGESTION_SELECTED_ONCE,
+
     NUM_FORM_EVENTS,
   };
 
   // For measuring the network request time of various Wallet API calls. See
   // WalletClient::RequestType.
   enum WalletApiCallMetric {
     UNKNOWN_API_CALL,  // Catch all. Should never be used.
     ACCEPT_LEGAL_DOCUMENTS,
     AUTHENTICATE_INSTRUMENT,
     GET_FULL_WALLET,
@@ skipping 193 matching lines @@
     void OnDidShowSuggestions();
 
     void OnDidSelectMaskedServerCardSuggestion();
 
     // In case of masked cards, caller must make sure this gets called before
     // the card is upgraded to a full card.
     void OnDidFillSuggestion(const CreditCard& credit_card);
 
     void OnDidFillSuggestion(const AutofillProfile& profile);
 
+    void OnWillSubmitForm();
+
     void OnDidSubmitForm();
 
    private:
     void Log(FormEvent event) const;
 
     bool is_for_credit_card_;
     bool is_server_data_available_;
     bool is_local_data_available_;
     bool has_logged_interacted_;
     bool has_logged_suggestions_shown_;
     bool has_logged_masked_server_card_suggestion_selected_;
     bool has_logged_suggestion_filled_;
     bool has_logged_submitted_;
     bool logged_suggestion_filled_was_server_data_;
     bool logged_suggestion_filled_was_masked_server_card_;
   };
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(AutofillMetrics);
 };
 
 }  // namespace autofill
 
 #endif  // COMPONENTS_AUTOFILL_CORE_BROWSER_AUTOFILL_METRICS_H_