Teach PasswordAutofillAgent sometimes match prefixes of usernames

chrome/renderer/autofill/password_autofill_agent_browsertest.cc

Index: chrome/renderer/autofill/password_autofill_agent_browsertest.cc
diff --git a/chrome/renderer/autofill/password_autofill_agent_browsertest.cc b/chrome/renderer/autofill/password_autofill_agent_browsertest.cc
index 9e449139f3ed44e4b3bc73bd4b187221b4573f60..551dd8a99578f6160c6503d954d913c96816d4bd 100644
--- a/chrome/renderer/autofill/password_autofill_agent_browsertest.cc
+++ b/chrome/renderer/autofill/password_autofill_agent_browsertest.cc
@@ -717,6 +717,53 @@ TEST_F(PasswordAutofillAgentTest,
                        UTF16ToUTF8(password3_), true);
 }
 
+// Fill a password field if the stored username is a prefix of username in
+// read-only field.
+TEST_F(PasswordAutofillAgentTest,
+       AutocompletePasswordForReadonlyUsernamePrefixMatched) {
+  base::string16 username_at = username3_ + base::UTF8ToUTF16("@example.com");
+  username_element_.SetValue(WebString::FromUTF16(username_at));
+  SetElementReadOnly(username_element_, true);
+
+  // Filled even though the username in the form is only a proper prefix of the
+  // stored username.
+  SimulateOnFillPasswordForm(fill_data_);
+  CheckTextFieldsState(UTF16ToUTF8(username_at), false, UTF16ToUTF8(password3_),
+                       true);
+}
+
+// Do not fill a password field if the stored username is a prefix without @
+// of username in read-only field.
+TEST_F(PasswordAutofillAgentTest,
+       DontAutocompletePasswordForReadonlyUsernamePrefixMatched) {
+  base::string16 prefilled_username =
+      username3_ + base::UTF8ToUTF16("example.com");
+  username_element_.SetValue(WebString::FromUTF16(prefilled_username));
+  SetElementReadOnly(username_element_, true);
+
+  // Filled even though the username in the form is only a proper prefix of the
+  // stored username.
+  SimulateOnFillPasswordForm(fill_data_);
+  CheckTextFieldsState(UTF16ToUTF8(prefilled_username), false, std::string(),
+                       false);
+}
+
+// Do not fill a password field if the field isn't readonly despite the stored
+// username is a prefix without @ of username in read-only field.
+TEST_F(
+    PasswordAutofillAgentTest,
+    DontAutocompletePasswordForNotReadonlyUsernameFieldEvenWhenPrefixMatched) {
+  base::string16 prefilled_username =
+      username3_ + base::UTF8ToUTF16("@example.com");
+  username_element_.SetValue(WebString::FromUTF16(prefilled_username));
+
+  // Filled even though the username in the form is only a proper prefix of the
+  // stored username.
+  SimulateOnFillPasswordForm(fill_data_);
+  CheckTextFieldsState(UTF16ToUTF8(prefilled_username), false, std::string(),
+                       false);
+}
+
 // If a username field is empty and readonly, don't autofill.
 TEST_F(PasswordAutofillAgentTest,
        NoAutocompletePasswordForReadonlyUsernameUnmatched) {