Use std::make_reverse_iterator in password_manager

This CL adds the first use of std::make_reverse_iterator, inside the
password_manager component at a place where it shortens an awkwardly
long for-loop header.

It also adds std::make_reverse_iterator to the allowed C++14 features.

Bug: 845426
Change-Id: Ief6983c167b3c85a7d52a25555e8157d4d0f0a1c
Reviewed-on: https://chromium-review.googlesource.com/1078758
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Commit-Queue: Vaclav Brozek <vabr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#562987}

components/password_manager/core/browser/form_parsing/form_parser.cc

@@ -326,9 +326,7 @@ const FormFieldData* FindUsernameFieldBaseHeuristics(
   const FormFieldData* focusable_username = nullptr;
   const FormFieldData* username = nullptr;
   // Do reverse search to find the closest candidates preceding the password.
-  for (auto it = std::reverse_iterator<
-           std::vector<const FormFieldData*>::const_iterator>(
-           first_relevant_password_it);
+  for (auto it = std::make_reverse_iterator(first_relevant_password_it);
        it != fields.rend(); ++it) {
     if ((*it)->form_control_type == "password")
       continue;

styleguide/c++/c++11.html

@@ -704,6 +704,14 @@ <h2 id="whitelist"><a name="library-whitelist-14"></a>C++14 Allowed Library Feat
 <td></td>
 </tr>
 
+<tr>
+<td>Reverse Iterator Adaptor</td>
+<td><code>std::make_reverse_iterator()</code></td>
+<td>For a given iterator, deduces the type of a corresponding reverse iterator and constructs it.</td>
+<td><a href="http://en.cppreference.com/w/cpp/iterator/make_reverse_iterator">std::make_reverse_iterator</a></td>
+<td>Useful to reduce boilerplate when constructing reverse iterators. The alternative is using <code>std::reverse_iterator<T>(i)</code> where <code>T</code> is the, usually long, type of the iterator <code>i</code>. <a href="https://groups.google.com/a/chromium.org/forum/#!topic/cxx/qOE1XA0b6Dk">Discussion thread</a></td>
+</tr>
+
 </tbody>
 </table>