PasswordStore: Clean up expectations about rewriting vectors of forms

chrome/browser/password_manager/password_store_x.h

Index: chrome/browser/password_manager/password_store_x.h
diff --git a/chrome/browser/password_manager/password_store_x.h b/chrome/browser/password_manager/password_store_x.h
index 17655338947e9e334451ecc023feb1e1f5824ae8..31c42e4babc2ba6138dba9fe29d97641bb2db1e7 100644
--- a/chrome/browser/password_manager/password_store_x.h
+++ b/chrome/browser/password_manager/password_store_x.h
@@ -58,12 +58,16 @@ class PasswordStoreX : public password_manager::PasswordStoreDefault {
         base::Time delete_end,
         password_manager::PasswordStoreChangeList* changes) = 0;
 
+    // The three methods below overwrite |forms| with all stored credentials
+    // matching |form|, all stored non-blacklisted credentials, and all stored
+    // blacklisted credentials, respectively. On success, they return true.
     virtual bool GetLogins(const autofill::PasswordForm& form,
-                           ScopedVector<autofill::PasswordForm>* forms) = 0;
+                           ScopedVector<autofill::PasswordForm>* forms)
+        WARN_UNUSED_RESULT = 0;
     virtual bool GetAutofillableLogins(
-        ScopedVector<autofill::PasswordForm>* forms) = 0;
-    virtual bool GetBlacklistLogins(
-        ScopedVector<autofill::PasswordForm>* forms) = 0;
+        ScopedVector<autofill::PasswordForm>* forms) WARN_UNUSED_RESULT = 0;
+    virtual bool GetBlacklistLogins(ScopedVector<autofill::PasswordForm>* forms)
+        WARN_UNUSED_RESULT = 0;
   };
 
   // Takes ownership of |login_db| and |backend|. |backend| may be NULL in which