[Mac][Material Design] Get Omnibox table width from dropdown window.

chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm

Index: chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm
diff --git a/chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm b/chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm
index e18b78eda1fb6de85f0e266464a4a411337319cf..7e92d3a7c48c2d2bbb5b5c24b307cad0d9f32e5d 100644
--- a/chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm
+++ b/chrome/browser/ui/cocoa/omnibox/omnibox_popup_view_mac.mm
@@ -260,7 +260,7 @@ void OmniboxPopupViewMac::PositionPopup(const CGFloat matrixHeight) {
   // In Material Design, the table is the width of the window. In non-MD,
   // calculate the width of the table based on backing out the popup's border
   // from the width of the field.
-  CGFloat table_width = NSWidth([background_view_ bounds]);
+  CGFloat table_width = NSWidth([[[field_ window] contentView] bounds]);
   bool is_mode_material = ui::MaterialDesignController::IsModeMaterial();
   if (!is_mode_material) {
     table_width = NSWidth([field_ bounds]);