Persist the choice of AutofillDataModel when using the requestAutocomplete dialog.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 42c4232821d8767ce899fc8aefb6189955e05728..5afea69a1054749d6543a15465ac05ba7b72b510 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1115,6 +1115,8 @@ const char kDefaultZoomLevel[] = "profile.default_zoom_level";
 // be displayed at the default zoom level.
 const char kPerHostZoomLevels[] = "profile.per_host_zoom_levels";
 
+const char kAutofillDialogAutofillDefault[] = "autofill.data_model_default";
+
 // Whether a user opted out of making purchases with Google Wallet; changed via
 // the autofill dialog's account chooser and set explicitly on dialog submission
 // (but not cancel). If this isn't set, the dialog assumes it's the first run.