No static destructors in IsCreditCardVerificationPasswordField

Currently, IsCreditCardVerificationPasswordField creates a static
string16 object. That involves a static destructor, which is forbidden
by the style guide:
https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables

This CL fixes that by using base::NoDestructor. It also restructures the
function slightly.

There should be no visible change caused by this CL.

Bug: 833838
Change-Id: Id879c5595113aae295e858bebf6cacc7f211b373
Reviewed-on: https://chromium-review.googlesource.com/1028272
Commit-Queue: Vaclav Brozek <vabr@chromium.org>
Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553797}

components/autofill/content/renderer/password_form_conversion_utils.cc

@@ -13,6 +13,7 @@
 #include "base/lazy_instance.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/no_destructor.h"
 #include "base/stl_util.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_split.h"
@@ -456,6 +457,13 @@ bool ScriptModifiedUsernameAcceptable(
   return false;
 }
 
+bool StringMatchesCVC(const base::string16& str) {
+  static const base::NoDestructor<base::string16> kCardCvcReCached(
+      base::UTF8ToUTF16(kCardCvcRe));
+
+  return MatchesPattern(str, *kCardCvcReCached);
+}
+
 // Get information about a login form encapsulated in a PasswordForm struct.
 // If an element of |form| has an entry in |nonscript_modified_values|, the
 // associated string is used instead of the element's value to create
@@ -974,11 +982,8 @@ bool IsCreditCardVerificationPasswordField(
     const blink::WebInputElement& field) {
   if (!field.IsPasswordFieldForAutofill())
     return false;
-
-  static const base::string16 kCardCvcReCached = base::UTF8ToUTF16(kCardCvcRe);
-
-  return MatchesPattern(field.GetAttribute("id").Utf16(), kCardCvcReCached) ||
-         MatchesPattern(field.GetAttribute("name").Utf16(), kCardCvcReCached);
+  return StringMatchesCVC(field.GetAttribute("id").Utf16()) ||
+         StringMatchesCVC(field.GetAttribute("name").Utf16());
 }
 
 std::string GetSignOnRealm(const GURL& origin) {