Prefer the exact match over prefix match for the password manager filling.

components/autofill/content/renderer/password_autofill_agent.cc

Index: components/autofill/content/renderer/password_autofill_agent.cc
diff --git a/components/autofill/content/renderer/password_autofill_agent.cc b/components/autofill/content/renderer/password_autofill_agent.cc
index e55f1988a3cea78d960e13538346351a51c9e673..ac1e4060717f3ffa5f834681e459db870d76cc5e 100644
--- a/components/autofill/content/renderer/password_autofill_agent.cc
+++ b/components/autofill/content/renderer/password_autofill_agent.cc
@@ -452,8 +452,14 @@ bool FillUserNameAndPassword(
   base::string16 username;
   base::string16 password;
 
-  FindMatchesByUsername(fill_data, current_username, exact_username_match,
-                        logger, &username, &password);
+  FindMatchesByUsername(fill_data, current_username,
+                        true /* exact_username_match */, logger, &username,
+                        &password);
+
+  if (!exact_username_match && password.empty()) {
+    FindMatchesByUsername(fill_data, current_username, exact_username_match,
+                          logger, &username, &password);
+  }
 
   if (password.empty())
     return false;