Have SearchProvider look up the omnibox start margin directly.

chrome/browser/ui/omnibox/omnibox_edit_model.cc

Index: chrome/browser/ui/omnibox/omnibox_edit_model.cc
diff --git a/chrome/browser/ui/omnibox/omnibox_edit_model.cc b/chrome/browser/ui/omnibox/omnibox_edit_model.cc
index d58aa08fffd06ae5dd364172ec45c67fb7cf5729..4ee0baf09bcd9a3ca909c61bd67523d2afd9959f 100644
--- a/chrome/browser/ui/omnibox/omnibox_edit_model.cc
+++ b/chrome/browser/ui/omnibox/omnibox_edit_model.cc
@@ -502,8 +502,7 @@ void OmniboxEditModel::StartAutocomplete(
       (has_selected_text && inline_autocomplete_text_.empty()) ||
       (paste_state_ != NONE),
       keyword_is_selected,
-      keyword_is_selected || allow_exact_keyword_match_,
-      controller_->GetOmniboxBounds().x());
+      keyword_is_selected || allow_exact_keyword_match_);
 }
 
 void OmniboxEditModel::StopAutocomplete() {