Measure how many times a generated password is deleted by autofilling

Bug: 880076
Change-Id: Ibd0f57fd3b0199c897a8b28bbf7f7a85f79693ac
Reviewed-on: https://chromium-review.googlesource.com/1195503
Commit-Queue: Ioana Pandele <ioanap@chromium.org>
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588409}

components/autofill/content/renderer/password_generation_agent.cc

@@ -285,8 +285,11 @@ void PasswordGenerationAgent::OnDynamicFormsSeen() {
 
 void PasswordGenerationAgent::OnFieldAutofilled(
     const WebInputElement& password_element) {
-  if (password_is_generated_ && generation_element_ == password_element)
+  if (password_is_generated_ && generation_element_ == password_element) {
+    password_generation::LogPasswordGenerationEvent(
+        password_generation::PASSWORD_DELETED_BY_AUTOFILLING);
     PasswordNoLongerGenerated();
+  }
 }
 
 void PasswordGenerationAgent::FindPossibleGenerationForm() {

components/autofill/core/common/password_generation_util.h

@@ -71,6 +71,10 @@ enum PasswordGenerationEvent {
   // Context menu with generation item was shown.
   PASSWORD_GENERATION_CONTEXT_MENU_SHOWN,
 
+  // The generated password was removed from the field because a credential
+  // was autofilled.
+  PASSWORD_DELETED_BY_AUTOFILLING,
+
   // Number of enum entries, used for UMA histogram reporting macros.
   EVENT_ENUM_COUNT
 };

tools/metrics/histograms/enums.xml

@@ -37194,6 +37194,7 @@ Called by update_net_trust_anchors.py.-->
   <int value="12" label="Generation triggered by autocomplete attributes"/>
   <int value="13" label="Generation item in the context menu accepted"/>
   <int value="14" label="Generation item in the context menu shown"/>
+  <int value="15" label="Generated password deleted by autofilling"/>
 </enum>
 
 <enum name="PasswordGenerationUserEvent">