Disable the Mac "Access Address Book" Autofill popup.

The intent of this patch is to create something small and harmless for merging to M38. The prompt will be reenabled as soon as the logic for showing it is updated.

BUG=408695
R=erikchen@chromium.org

Review URL: https://codereview.chromium.org/535243002

Cr-Commit-Position: refs/heads/master@{#293320}

components/autofill/core/browser/autofill_external_delegate.cc

@@ -117,6 +117,8 @@ void AutofillExternalDelegate::OnSuggestionsReturned(
   // updated to match.
   InsertDataListValues(&values, &labels, &icons, &ids);
 
+// Temporarily disabled. See http://crbug.com/408695
+#if 0
 #if defined(OS_MACOSX) && !defined(OS_IOS)
   if (values.empty() &&
       manager_->ShouldShowAccessAddressBookSuggestion(query_form_,
@@ -130,6 +132,7 @@ void AutofillExternalDelegate::OnSuggestionsReturned(
     EmitHistogram(SHOWED_ACCESS_ADDRESS_BOOK_ENTRY);
   }
 #endif  // defined(OS_MACOSX) && !defined(OS_IOS)
+#endif
 
   if (values.empty()) {
     // No suggestions, any popup currently showing is obsolete.