[Autofill] Use const string16& parameter type, removing the need for explicit move

As brought up in https://codereview.chromium.org/1622073002/

BUG=None

Review URL: https://codereview.chromium.org/1624373004

Cr-Commit-Position: refs/heads/master@{#371518}

components/autofill/core/browser/autofill_field.h

@@ -53,8 +53,8 @@ class AutofillField : public FormFieldData {
   void set_previously_autofilled(bool previously_autofilled) {
     previously_autofilled_ = previously_autofilled;
   }
-  void set_parseable_name(base::string16 parseable_name) {
-    parseable_name_ = std::move(parseable_name);
+  void set_parseable_name(const base::string16& parseable_name) {
+    parseable_name_ = parseable_name;
   }
 
   // This function automatically chooses between server and heuristic autofill